CC-4663: Smart Blocks -> Deleting a track in smart block from library gives error

-fixed
-tracks with undefined mime type were not handled properly

airtime_mvc/public/js/airtime/library/spl.js

@@ -369,6 +369,9 @@ var AIRTIME = (function(AIRTIME){
         $.each($("div .big_play"), function(index, value){
             if ($(value).attr('blockId') === undefined) {
                 var mime = $(value).attr("data-mime-type");
+                //If mime is undefined it is likely because the file was
+                //deleted from the library. This case is handled in mod.onReady()
+                if (mime !== undefined) {
                     if (isAudioSupported(mime)) {
                         $(value).bind("click", openAudioPreview);
                     } else {
@@ -393,6 +396,7 @@ var AIRTIME = (function(AIRTIME){
                             },
                         }) 
                     }
+                }
             } else {
                 if ($(value).attr('blocktype') === 'dynamic') {
                     $(value).attr("class", "big_play_disabled dark_class");