[Modify] Polish it

websocket-sharp/Net/ResponseStream.cs

@@ -306,7 +306,14 @@ namespace WebSocketSharp.Net
 
     public override void Flush ()
     {
-      if (!_disposed && (_sendChunked || _response.SendChunked))
+      if (_disposed)
+        return;
+
+      var sendChunked = _sendChunked || _response.SendChunked;
+
+      if (!sendChunked)
+        return;
+
       flush (false);
     }