Remove the nullable disable annotation.

Also, mark as nullable for some properties.

osu.Game/Rulesets/Mods/DifficultyBindable.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using osu.Framework.Bindables;
 using osu.Game.Beatmaps;
@@ -29,7 +27,7 @@ namespace osu.Game.Rulesets.Mods
         /// <summary>
         /// A function that can extract the current value of this setting from a beatmap difficulty for display purposes.
         /// </summary>
-        public Func<IBeatmapDifficultyInfo, float> ReadCurrentFromDifficulty;
+        public Func<IBeatmapDifficultyInfo, float>? ReadCurrentFromDifficulty;
 
         public float Precision
         {

osu.Game/Rulesets/Mods/IApplicableAfterBeatmapConversion.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Beatmaps;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/IApplicableFailOverride.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 namespace osu.Game.Rulesets.Mods
 {
     /// <summary>

osu.Game/Rulesets/Mods/IApplicableMod.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 namespace osu.Game.Rulesets.Mods
 {
     /// <summary>

osu.Game/Rulesets/Mods/IApplicableToAudio.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 namespace osu.Game.Rulesets.Mods
 {
     public interface IApplicableToAudio : IApplicableToTrack, IApplicableToSample

osu.Game/Rulesets/Mods/IApplicableToBeatmap.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Beatmaps;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/IApplicableToBeatmapConverter.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Beatmaps;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/IApplicableToBeatmapProcessor.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Beatmaps;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/IApplicableToDifficulty.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Beatmaps;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/IApplicableToDrawableHitObject.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Rulesets.Objects.Drawables;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/IApplicableToDrawableHitObjects.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using osu.Framework.Extensions.IEnumerableExtensions;

osu.Game/Rulesets/Mods/IApplicableToDrawableRuleset.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Rulesets.Objects;
 using osu.Game.Rulesets.UI;
 

osu.Game/Rulesets/Mods/IApplicableToHUD.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Screens.Play;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/IApplicableToHealthProcessor.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Rulesets.Scoring;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/IApplicableToHitObject.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Rulesets.Objects;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/IApplicableToPlayer.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Screens.Play;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/IApplicableToRate.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 namespace osu.Game.Rulesets.Mods
 {
     /// <summary>

osu.Game/Rulesets/Mods/IApplicableToSample.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Framework.Audio;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/IApplicableToScoreProcessor.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Rulesets.Scoring;
 using osu.Game.Scoring;
 

osu.Game/Rulesets/Mods/IApplicableToTrack.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Framework.Audio;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/ICreateReplay.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using osu.Game.Beatmaps;

osu.Game/Rulesets/Mods/ICreateReplayData.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System.Collections.Generic;
 using osu.Game.Beatmaps;
 using osu.Game.Online.API.Requests.Responses;
@@ -45,7 +43,7 @@ namespace osu.Game.Rulesets.Mods
         /// </summary>
         public readonly ModCreatedUser User;
 
-        public ModReplayData(Replay replay, ModCreatedUser user = null)
+        public ModReplayData(Replay replay, ModCreatedUser? user = null)
         {
             Replay = replay;
             User = user ?? new ModCreatedUser();

osu.Game/Rulesets/Mods/IHasSeed.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Framework.Bindables;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/IMod.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using osu.Framework.Graphics.Sprites;
 

osu.Game/Rulesets/Mods/IReadFromConfig.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Configuration;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/IUpdatableByPlayfield.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Rulesets.UI;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/MetronomeBeat.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Framework.Audio;
 using osu.Framework.Audio.Track;
 using osu.Framework.Bindables;

osu.Game/Rulesets/Mods/Mod.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -117,7 +115,7 @@ namespace osu.Game.Rulesets.Mods
         [JsonIgnore]
         public virtual Type[] IncompatibleMods => Array.Empty<Type>();
 
-        private IReadOnlyList<IBindable> settingsBacking;
+        private IReadOnlyList<IBindable>? settingsBacking;
 
         /// <summary>
         /// A list of the all <see cref="IBindable"/> settings within this mod.

osu.Game/Rulesets/Mods/ModAdaptiveSpeed.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -79,7 +77,7 @@ namespace osu.Game.Rulesets.Mods
         // Apply a fixed rate change when missing, allowing the player to catch up when the rate is too fast.
         private const double rate_change_on_miss = 0.95d;
 
-        private IAdjustableAudioComponent track;
+        private IAdjustableAudioComponent? track;
         private double targetRate = 1d;
 
         /// <summary>

osu.Game/Rulesets/Mods/ModAutoplay.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using osu.Framework.Graphics.Sprites;

osu.Game/Rulesets/Mods/ModBarrelRoll.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using osu.Framework.Bindables;
 using osu.Framework.Extensions;

osu.Game/Rulesets/Mods/ModBlockFail.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Framework.Bindables;
 using osu.Game.Configuration;
 using osu.Game.Screens.Play;

osu.Game/Rulesets/Mods/ModCinema.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Linq;
 using osu.Framework.Graphics.Sprites;

osu.Game/Rulesets/Mods/ModClassic.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Framework.Graphics.Sprites;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/ModDaycore.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Framework.Audio;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics.Sprites;

osu.Game/Rulesets/Mods/ModDifficultyAdjust.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Linq;
 using osu.Framework.Bindables;

osu.Game/Rulesets/Mods/ModDoubleTime.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Framework.Bindables;
 using osu.Framework.Graphics.Sprites;
 using osu.Game.Configuration;

osu.Game/Rulesets/Mods/ModEasy.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using osu.Framework.Graphics.Sprites;
 using osu.Game.Beatmaps;

osu.Game/Rulesets/Mods/ModEasyWithExtraLives.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using Humanizer;
 using osu.Framework.Bindables;
 using osu.Game.Beatmaps;

osu.Game/Rulesets/Mods/ModExtensions.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System.Collections.Generic;
 using osu.Game.Beatmaps;
 using osu.Game.Online.API.Requests.Responses;

osu.Game/Rulesets/Mods/ModFailCondition.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using osu.Framework.Bindables;
 using osu.Game.Configuration;

osu.Game/Rulesets/Mods/ModFlashlight.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using osu.Framework.Allocation;

osu.Game/Rulesets/Mods/ModHalfTime.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Framework.Bindables;
 using osu.Framework.Graphics.Sprites;
 using osu.Game.Configuration;

osu.Game/Rulesets/Mods/ModHardRock.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using osu.Framework.Graphics.Sprites;
 using osu.Game.Beatmaps;

osu.Game/Rulesets/Mods/ModHidden.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Game.Graphics;
 using osu.Framework.Graphics.Sprites;
 using osu.Game.Rulesets.Scoring;

osu.Game/Rulesets/Mods/ModMirror.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 namespace osu.Game.Rulesets.Mods
 {
     public abstract class ModMirror : Mod

osu.Game/Rulesets/Mods/ModMuted.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System.Linq;
 using osu.Framework.Audio;
 using osu.Framework.Bindables;

osu.Game/Rulesets/Mods/ModNightcore.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Framework.Allocation;
 using osu.Framework.Audio;
 using osu.Framework.Audio.Track;
@@ -57,10 +55,10 @@ namespace osu.Game.Rulesets.Mods
 
         public class NightcoreBeatContainer : BeatSyncedContainer
         {
-            private PausableSkinnableSound hatSample;
+            private PausableSkinnableSound? hatSample;
-            private PausableSkinnableSound clapSample;
+            private PausableSkinnableSound? clapSample;
-            private PausableSkinnableSound kickSample;
+            private PausableSkinnableSound? kickSample;
-            private PausableSkinnableSound finishSample;
+            private PausableSkinnableSound? finishSample;
 
             private int? firstBeat;
 

osu.Game/Rulesets/Mods/ModNoFail.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using osu.Framework.Graphics.Sprites;
 using osu.Game.Graphics;

osu.Game/Rulesets/Mods/ModNoMod.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Framework.Graphics.Sprites;
 
 namespace osu.Game.Rulesets.Mods

osu.Game/Rulesets/Mods/ModNoScope.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics;

osu.Game/Rulesets/Mods/ModPerfect.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Linq;
 using osu.Framework.Graphics.Sprites;

osu.Game/Rulesets/Mods/ModRandom.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using osu.Framework.Bindables;
 using osu.Framework.Graphics.Sprites;
 using osu.Game.Configuration;

osu.Game/Rulesets/Mods/ModRateAdjust.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using osu.Framework.Audio;
 using osu.Framework.Bindables;

osu.Game/Rulesets/Mods/ModRelax.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using osu.Framework.Graphics.Sprites;
 using osu.Game.Graphics;

osu.Game/Rulesets/Mods/ModSuddenDeath.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Linq;
 using osu.Framework.Graphics.Sprites;

osu.Game/Rulesets/Mods/ModTimeRamp.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Linq;
 using osu.Framework.Audio;
@@ -46,7 +44,7 @@ namespace osu.Game.Rulesets.Mods
             Precision = 0.01,
         };
 
-        private IAdjustableAudioComponent track;
+        private IAdjustableAudioComponent? track;
 
         protected ModTimeRamp()
         {

osu.Game/Rulesets/Mods/ModType.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 namespace osu.Game.Rulesets.Mods
 {
     public enum ModType

osu.Game/Rulesets/Mods/ModWindDown.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Linq;
 using osu.Framework.Bindables;

osu.Game/Rulesets/Mods/ModWindUp.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Linq;
 using osu.Framework.Bindables;

osu.Game/Rulesets/Mods/ModWithVisibilityAdjustment.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System.Collections.Generic;
 using osu.Framework.Bindables;
 using osu.Game.Beatmaps;
@@ -21,7 +19,7 @@ namespace osu.Game.Rulesets.Mods
         /// <summary>
         /// The first adjustable object.
         /// </summary>
-        protected HitObject FirstObject { get; private set; }
+        protected HitObject? FirstObject { get; private set; }
 
         /// <summary>
         /// Whether the visibility of <see cref="FirstObject"/> should be increased.
@@ -59,7 +57,7 @@ namespace osu.Game.Rulesets.Mods
         {
             FirstObject = getFirstAdjustableObjectRecursive(beatmap.HitObjects);
 
-            HitObject getFirstAdjustableObjectRecursive(IReadOnlyList<HitObject> hitObjects)
+            HitObject? getFirstAdjustableObjectRecursive(IReadOnlyList<HitObject> hitObjects)
             {
                 foreach (var h in hitObjects)
                 {
@@ -93,7 +91,7 @@ namespace osu.Game.Rulesets.Mods
         /// <param name="toCheck">The <see cref="HitObject"/> to check.</param>
         /// <param name="target">The <see cref="HitObject"/> which may be equal to or contain <paramref name="toCheck"/> as a nested object.</param>
         /// <returns>Whether <paramref name="toCheck"/> is equal to or nested within <paramref name="target"/>.</returns>
-        private bool isObjectEqualToOrNestedIn(HitObject toCheck, HitObject target)
+        private bool isObjectEqualToOrNestedIn(HitObject toCheck, HitObject? target)
         {
             if (target == null)
                 return false;

osu.Game/Rulesets/Mods/MultiMod.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Linq;
 

osu.Game/Rulesets/Mods/UnknownMod.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 namespace osu.Game.Rulesets.Mods
 {
     public class UnknownMod : Mod