[Modify] Polish it

websocket-sharp/WebSocket.cs

@@ -2511,7 +2511,8 @@ namespace WebSocketSharp
           }
 
           var name = _compression.ToExtensionString ();
-          var invalid = ext.SplitHeaderValue (';').Contains (
+
+          var isInvalid = ext.SplitHeaderValue (';').Contains (
                             t => {
                               t = t.Trim ();
 
@@ -2523,7 +2524,7 @@ namespace WebSocketSharp
                             }
                           );
 
-          if (invalid)
+          if (isInvalid)
             return false;
 
           compRequested = false;