fix: networklist editor memory leak

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -15,6 +15,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 ### Fixed
 
+- Fixed issue where `NetworkList` properties on in-scene placed `NetworkObject`s could cause small memory leaks when entering playmode. (#3147)
 - Fixed in-scene `NertworkObject` synchronization issue when loading a scene with currently connected clients connected to a session created by a `NetworkManager` started as a server (i.e. not as a host). (#3133)
 - Fixed issue where a `NetworkManager` started as a server would not add itself as an observer to in-scene placed `NetworkObject`s instantiated and spawned by a scene loading event. (#3133)
 - Fixed issue where spawning a player using `NetworkObject.InstantiateAndSpawn` or `NetworkSpawnManager.InstantiateAndSpawn` would not update the `NetworkSpawnManager.PlayerObjects` or assign the newly spawned player to the `NetworkClient.PlayerObject`. (#3122)

com.unity.netcode.gameobjects/Runtime/NetworkVariable/Collections/NetworkList.cs

@@ -50,6 +50,11 @@ public NetworkList(IEnumerable<T> values = default,
             }
         }
 
+        ~NetworkList()
+        {
+            Dispose();
+        }
+
         /// <inheritdoc />
         public override void ResetDirty()
         {
@@ -624,8 +629,16 @@ public int LastModifiedTick
         /// </summary>
         public override void Dispose()
         {
-            m_List.Dispose();
-            m_DirtyEvents.Dispose();
+            if (m_List.IsCreated)
+            {
+                m_List.Dispose();
+            }
+
+            if (m_DirtyEvents.IsCreated)
+            {
+                m_DirtyEvents.Dispose();
+            }
+
             base.Dispose();
         }
     }