unbind all event handlers to video in clean-up method

padmaTexts/static/js/views/sidebar.js

@@ -217,6 +217,7 @@ function setupPadmaLink(videoObj, data) {
 // parameter is a padmaVideo object.
 function cleanupVideo(videoObj) {
   $('video')[0].pause();
+  $('video').unbind("play").unbind("ended").unbind("loadedmetadata");
   $('video').attr("src", "");
   clearInterval(videoObj.interval);
   $('.padmaViewer').remove();