[Modify] Polish it

websocket-sharp/Net/HttpUtility.cs

@@ -1199,11 +1199,10 @@ namespace WebSocketSharp.Net
       if (count < 0 || count > len - offset)
         throw new ArgumentOutOfRangeException ("count");
 
-      if (encoding == null)
-        encoding = Encoding.UTF8;
-
       return count > 0
-             ? encoding.GetString (urlDecodeToBytes (bytes, offset, count))
+             ? (encoding ?? Encoding.UTF8).GetString (
+                 urlDecodeToBytes (bytes, offset, count)
+               )
              : String.Empty;
     }