some fix

Assets/UniRx.Async/Internal/ContinuationQueue.cs

@@ -6,7 +6,7 @@ using System.Threading;
 
 namespace UniRx.Async.Internal
 {
-    internal class ContinuationQueue
+    internal sealed class ContinuationQueue
     {
         const int MaxArrayLength = 0X7FEFFFFF;
         const int InitialSize = 16;

Assets/UniRx.Async/UniTaskCompletionSource.cs

@@ -178,7 +178,7 @@ namespace UniRx.Async
         public TResult GetResult(short token)
         {
             ValidateToken(token);
-            if (!(completedCount == 0))
+            if (completedCount == 0)
             {
                 throw new InvalidOperationException("not yet completed.");
             }