diff --git a/osu.Desktop/OsuGameDesktop.cs b/osu.Desktop/OsuGameDesktop.cs
index 9351e17419..5f74883803 100644
--- a/osu.Desktop/OsuGameDesktop.cs
+++ b/osu.Desktop/OsuGameDesktop.cs
@@ -59,7 +59,7 @@ namespace osu.Desktop
             try
             {
                 using (RegistryKey key = Registry.ClassesRoot.OpenSubKey("osu"))
-                    stableInstallPath = key?.OpenSubKey(@"shell\open\command")?.GetValue(string.Empty).ToString().Split('"')[1].Replace("osu!.exe", "");
+                    stableInstallPath = key?.OpenSubKey(@"shell\open\command")?.GetValue(string.Empty).ToString()?.Split('"')[1].Replace("osu!.exe", "");
 
                 if (checkExists(stableInstallPath))
                     return stableInstallPath;
diff --git a/osu.Game.Tests/Chat/MessageFormatterTests.cs b/osu.Game.Tests/Chat/MessageFormatterTests.cs
index fbb0416c45..d1a859c84b 100644
--- a/osu.Game.Tests/Chat/MessageFormatterTests.cs
+++ b/osu.Game.Tests/Chat/MessageFormatterTests.cs
@@ -428,23 +428,23 @@ namespace osu.Game.Tests.Chat
             Assert.AreEqual(5, result.Links.Count);
 
             Link f = result.Links.Find(l => l.Url == "https://osu.ppy.sh/wiki/wiki links");
-            Assert.AreEqual(44, f.Index);
+            Assert.AreEqual(44, f!.Index);
             Assert.AreEqual(10, f.Length);
 
             f = result.Links.Find(l => l.Url == "http://www.simple-test.com");
-            Assert.AreEqual(10, f.Index);
+            Assert.AreEqual(10, f!.Index);
             Assert.AreEqual(11, f.Length);
 
             f = result.Links.Find(l => l.Url == "http://google.com");
-            Assert.AreEqual(97, f.Index);
+            Assert.AreEqual(97, f!.Index);
             Assert.AreEqual(4, f.Length);
 
             f = result.Links.Find(l => l.Url == "https://osu.ppy.sh");
-            Assert.AreEqual(78, f.Index);
+            Assert.AreEqual(78, f!.Index);
             Assert.AreEqual(18, f.Length);
 
             f = result.Links.Find(l => l.Url == "\uD83D\uDE12");
-            Assert.AreEqual(101, f.Index);
+            Assert.AreEqual(101, f!.Index);
             Assert.AreEqual(3, f.Length);
         }
 
diff --git a/osu.Game.Tests/Visual/UserInterface/TestSceneOsuIcon.cs b/osu.Game.Tests/Visual/UserInterface/TestSceneOsuIcon.cs
index 061039b297..246eb119e8 100644
--- a/osu.Game.Tests/Visual/UserInterface/TestSceneOsuIcon.cs
+++ b/osu.Game.Tests/Visual/UserInterface/TestSceneOsuIcon.cs
@@ -45,7 +45,7 @@ namespace osu.Game.Tests.Visual.UserInterface
             });
 
             foreach (var p in typeof(OsuIcon).GetProperties(BindingFlags.Public | BindingFlags.Static))
-                flow.Add(new Icon($"{nameof(OsuIcon)}.{p.Name}", (IconUsage)p.GetValue(null)));
+                flow.Add(new Icon($"{nameof(OsuIcon)}.{p.Name}", (IconUsage)p.GetValue(null)!));
 
             AddStep("toggle shadows", () => flow.Children.ForEach(i => i.SpriteIcon.Shadow = !i.SpriteIcon.Shadow));
             AddStep("change icons", () => flow.Children.ForEach(i => i.SpriteIcon.Icon = new IconUsage((char)(i.SpriteIcon.Icon.Icon + 1))));
diff --git a/osu.Game/IO/Serialization/Converters/TypedListConverter.cs b/osu.Game/IO/Serialization/Converters/TypedListConverter.cs
index f98fa05821..ddfdf08f52 100644
--- a/osu.Game/IO/Serialization/Converters/TypedListConverter.cs
+++ b/osu.Game/IO/Serialization/Converters/TypedListConverter.cs
@@ -41,13 +41,25 @@ namespace osu.Game.IO.Serialization.Converters
             var list = new List<T>();
 
             var obj = JObject.Load(reader);
-            var lookupTable = serializer.Deserialize<List<string>>(obj["$lookup_table"].CreateReader());
 
-            foreach (var tok in obj["$items"])
+            if (!obj.TryGetValue("$lookup_table", out var lookupTableToken) || lookupTableToken == null)
+                return list;
+
+            var lookupTable = serializer.Deserialize<List<string>>(lookupTableToken.CreateReader());
+            if (lookupTable == null)
+                return list;
+
+            if (!obj.TryGetValue("$items", out var itemsToken) || itemsToken == null)
+                return list;
+
+            foreach (var tok in itemsToken)
             {
                 var itemReader = tok.CreateReader();
 
-                var typeName = lookupTable[(int)tok["$type"]];
+                if (!obj.TryGetValue("$type", out var typeToken) || typeToken == null)
+                    throw new JsonException("Expected $type token.");
+
+                var typeName = lookupTable[(int)typeToken];
                 var instance = (T)Activator.CreateInstance(Type.GetType(typeName));
                 serializer.Populate(itemReader, instance);
 
diff --git a/osu.Game/Online/API/APIAccess.cs b/osu.Game/Online/API/APIAccess.cs
index 4945f7f185..f9e2da9af8 100644
--- a/osu.Game/Online/API/APIAccess.cs
+++ b/osu.Game/Online/API/APIAccess.cs
@@ -250,7 +250,7 @@ namespace osu.Game.Online.API
             {
                 try
                 {
-                    return JObject.Parse(req.GetResponseString()).SelectToken("form_error", true).ToObject<RegistrationRequest.RegistrationRequestErrors>();
+                    return JObject.Parse(req.GetResponseString()).SelectToken("form_error", true)!.ToObject<RegistrationRequest.RegistrationRequestErrors>();
                 }
                 catch
                 {