[Modify] Polish it

websocket-sharp/Net/HttpListener.cs

@@ -566,24 +566,22 @@ namespace WebSocketSharp.Net
 
     internal HttpListenerAsyncResult BeginGetContext (HttpListenerAsyncResult asyncResult)
     {
-      // Lock _ctxRegistrySync early to avoid race conditions.
       lock (_ctxRegistrySync) {
         if (!_listening)
           throw new HttpListenerException (995);
 
-        lock (_waitQueueSync) {
         var ctx = getContextFromQueue ();
-          if (ctx != null) {
-            asyncResult.Complete (ctx, true);
-            return asyncResult;
-          }
-
+        if (ctx == null) {
+          lock (_waitQueueSync)
             _waitQueue.Add (asyncResult);
         }
+        else {
+          asyncResult.Complete (ctx, true);
         }
 
         return asyncResult;
       }
+    }
 
     internal void CheckDisposed ()
     {