When protocols is undefined do not pass it to new WebSocket()

In this code when protocols is undefined as it is when using socket.io.
```
window.WebSocket = (url, protocols) =>
    req = new _WebSocket(url, protocols)
````

It will insert a header(below) into the request causing it to fail
```
Sec-WebSocket-Protocol: undefined 
```

This should allow the trackWebSockets option to be renabled by default