[niclas-bolle]

Problem

When a Reference<Texture2D> is garbage-collected without Dispose(), ~Reference() runs Dispose() → ImageLoader.ClearMemoryCache(url) on the GC finalizer thread. This throws:

InvalidOperationException: EnsureRunningOnMainThread can only be called from the main thread
UnityEngine.Object.EnsureRunningOnMainThread ()
UnityEngine.Object.GetInstanceID ()
UnityEngine.Object.IsNativeObjectAlive (UnityEngine.Object o)
UnityEngine.Object.CompareBaseObjects (UnityEngine.Object lhs, UnityEngine.Object rhs)
UnityEngine.Object.op_Equality (UnityEngine.Object x, UnityEngine.Object y)
Extensions.Unity.ImageLoader.InternalExtensions.IsNull (UnityEngine.Object obj)
Extensions.Unity.ImageLoader.FutureTexture.ReleaseMemoryTexture (UnityEngine.Texture2D obj, Extensions.Unity.ImageLoader.DebugLevel logLevel)
Extensions.Unity.ImageLoader.Safe.Run[T1,T2] (...)
Extensions.Unity.ImageLoader.Future`1:ClearMemoryCache(String, Action`2, DebugLevel)
Extensions.Unity.ImageLoader.ImageLoader:ClearMemoryCache(String)
Extensions.Unity.ImageLoader.Reference`1:Dispose()
Extensions.Unity.ImageLoader.Reference`1:Finalize()

ReleaseMemoryTexture already handles the off-main-thread case by posting DestroyImmediate to the main thread via UniTask.Post. But the pre-check right before the post calls IsNull(), which uses Unity's overloaded == and throws off the main thread. Safe.Run catches the exception. By then ClearMemoryCache has already removed the entry from the memory cache, so the texture is never destroyed and leaks. ReleaseMemorySprite has the same pre-check.

Fix

In the off-main-thread branch only, the pre-check now uses ReferenceEquals(obj, null). The UniTask.Post callback still runs the full IsNull() check on the main thread before destroying. The main-thread branch is unchanged.

Testing

We run this patch in a production Unity 6 (6000.3) project. Before it, the exception above showed up regularly in the Editor during Play Mode whenever a GC finalized a leaked Reference.

With the patch applied, I checked it deterministically: I created a Reference for a cached texture, dropped it without Dispose(), and forced GC.Collect(); GC.WaitForPendingFinalizers();. There was no exception. Right after the GC the cache entry was gone but the texture was still alive, which shows the destroy was posted from the finalizer thread. The texture was destroyed on the next main-thread frame.