Fix connecting to a websocket the second time returning "window.document is undefined"

window.document is setup the first time, then cleared after start() is called... we need to reset up the window.document each time start() is called

Author: mlabrum

src/index.js

@@ -29,6 +29,7 @@ export default {
     const hubConnectionFunc = signalRHubConnectionFunc(serverUrl, options);
     const originalStart = hubConnectionFunc.start;
     hubConnectionFunc.start = (...args) => {
+      window.document = window.document || { readyState: 'complete' };
       window.document.createElement = () => {
         return {
           protocol,