Fix https://github.com/HenningM/express-ws/issues/64 by setting a str…

[mdvanes]

…ing in the _header property of the response.

I also ran into this issue: #64
According to dougwilson #64 (comment) who seems to be an Express maintainer, the problem was this missing property.

Now, I have done this patch without a thorough understanding of your library, and without diving deeply into dougwilson's answer, but it seems to fix the problem for me.

Maybe this will help some other people, too.

[salzig]

just as a note, i still get this error, unless i move the dummyREsponse._header out and before the conditional.

like so:

      dummyResponse._header = '';
      if (statusCode > 200) {
        /* Something in the middleware chain signalled an error. */	        /* Something in the middleware chain signalled an error. */
        socket.close();	        socket.close();
      }

[mdvanes]

This was merged and I have been using version 4.x in production ever since and that solved my issue. @salzig Could you log the value of statusCode? Maybe you get an sub 200 code or (more likely) an undefined?