Fix undisposed Realm subscription

osu.Game/Overlays/Toolbar/ToolbarButton.cs

@@ -1,6 +1,7 @@
 // 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.
 
+using System;
 using System.Linq;
 using osu.Framework.Allocation;
 using osu.Framework.Extensions.Color4Extensions;
@@ -77,6 +78,8 @@ namespace osu.Game.Overlays.Toolbar
 
         protected readonly Container BackgroundContent;
 
+        private IDisposable? realmSubscription;
+
         [Resolved]
         private RealmAccess realm { get; set; } = null!;
 
@@ -184,7 +187,8 @@ namespace osu.Game.Overlays.Toolbar
         {
             if (Hotkey != null)
             {
-                realm.SubscribeToPropertyChanged(r => r.All<RealmKeyBinding>().FirstOrDefault(rkb => rkb.RulesetName == null && rkb.ActionInt == (int)Hotkey.Value), kb => kb.KeyCombinationString, updateKeyBindingTooltip);
+                realmSubscription = realm.SubscribeToPropertyChanged(r => r.All<RealmKeyBinding>().FirstOrDefault(rkb => rkb.RulesetName == null && rkb.ActionInt == (int)Hotkey.Value),
+                    kb => kb.KeyCombinationString, updateKeyBindingTooltip);
             }
         }
 
@@ -234,6 +238,13 @@ namespace osu.Game.Overlays.Toolbar
                 ? $" ({keyBindingString})"
                 : string.Empty;
         }
+
+        protected override void Dispose(bool isDisposing)
+        {
+            base.Dispose(isDisposing);
+
+            realmSubscription?.Dispose();
+        }
     }
 
     public partial class OpaqueBackground : Container