check that there are audio textTracks before trying to use them for #1871

modules/islandora_audio/js/audio.js

@@ -21,12 +21,14 @@
     function init(context,settings){
         if (!initialized){
             initialized = true;
+            if ($('audio')[0].textTracks.length > 0) {
                 $('audio')[0].textTracks[0].oncuechange = function() {
                     var currentCue = this.activeCues[0].text;
                     $('#audioTrack').html(currentCue);
                 }
             }
         }
+    }
     Drupal.Audio = Drupal.Audio || {};
 
     /**