CC-4166: Playlist Builder -> Regular Playlist : clicking Fade in/out button for a empty playlist will cause PHP Fatal Error

- fixed. Not displaying fade setting button if the playst/smartplaylist
is empty.

airtime_mvc/public/js/airtime/playlist/smart_playlistbuilder.js

@@ -181,6 +181,7 @@ function setSmartPlaylistEvents() {
         enableLoadingIcon();
         $.post(save_action, {format: "json", data: data, obj_id: obj_id}, function(data){
             callback(data, "save");
+            setFadeIcon();
             disableLoadingIcon();
         });
     });
@@ -254,6 +255,16 @@ function setStaticLengthHolder(lenVal) {
 }
 */
 
+function setFadeIcon(){
+    var contents = $("#spl_sortable");
+    var show = contents.is(":visible");
+    if (show) {
+        $("#spl_crossfade").show();
+    } else {
+        $("#spl_crossfade").hide();
+    }
+}
+
 /* This function appends a '+' button for the last
  * modifier row of each criteria.
  * If there are no modifier rows, the '+' button