Merge pull request #68 from unclespode/patch-2

Fix: Cannot read property 'headers' of undefined

Author: driverdan

lib/XMLHttpRequest.js

@@ -205,6 +205,8 @@ exports.XMLHttpRequest = function() {
   this.getResponseHeader = function(header) {
     if (typeof header === "string"
       && this.readyState > this.OPENED
+      && response
+      && response.headers
       && response.headers[header.toLowerCase()]
       && !errorFlag
     ) {