Merge branch 'master' of github.com:igrigorik/videospeed

inject.js

@@ -159,7 +159,7 @@ chrome.extension.sendMessage({}, function(response) {
       return;
 
     var readyStateCheckInterval = setInterval(function() {
-      if (document.readyState === 'complete') {
+      if (document && document.readyState === 'complete') {
         clearInterval(readyStateCheckInterval);
         initializeNow(document);
       }