Scheduler: RequiresMarshalling samples current thread just once

Author: AshleighAdams

src/CoroutineScheduler/Scheduler.cs

@@ -63,7 +63,11 @@ public Scheduler()
 	private ContextCallback? Runner { get; set; }
 
 	private int? ResumingOnThread { get; set; }
-	private bool RequiresMarshalling => ResumingOnThread is null || ResumingOnThread.Value != Thread.CurrentThread.ManagedThreadId;
+	private bool RequiresMarshalling => ResumingOnThread switch
+	{
+		int resumingThread => resumingThread != Thread.CurrentThread.ManagedThreadId,
+		_ => true,
+	};
 
 	/// <summary>
 	/// Resume any tasks that are at the point of invocation are currently awaiting `Yield()`, and <br />