Check if the cue has changed before updating the HTML. (#853)

modules/islandora_audio/js/audio.js

@@ -23,12 +23,14 @@
             initialized = true;
             if ($('audio')[0].textTracks.length > 0) {
                 $('audio')[0].textTracks[0].oncuechange = function() {
+                  if (this.activeCues.length > 0) {
                     var currentCue = this.activeCues[0].text;
                     $('#audioTrack').html(currentCue);
                   }
                 }
             }
         }
+    }
     Drupal.Audio = Drupal.Audio || {};
 
     /**