websocket example connection error

I've manager to reproduce one of these issues using a current build on linux.

vue native sockets in chrome browser -> Backend Espruino WS server.

If protocol is specified, then all is well:

const ws = new WebSocket('ws://192.168.1.203:8000', 'protocolOne');

However, if this is defaulted, ws.js on the espruino sends as a header:

Sec-WebSocket-Protocol: undefined

this test seems to be failing:
https://github.com/espruino/EspruinoDocs/blob/master/modules/ws.js#L196-L197

if (this.protocol)
    socketHeader.push("Sec-WebSocket-Protocol: "+this.protocol);

in the constructor we have:
https://github.com/espruino/EspruinoDocs/blob/master/modules/ws.js#L76-L86
this.protocol = options.protocol;

So it seems this is setting this.protocol=undefined.

What is the cleanest way to fix?

if ( typeof(this.protocol) != 'undefined' )