Showing Layer --> Null javascript error

Hello, started having a weird issue out of the blue. I have a slide that is shown as a Light Box. The light box slide has a condition to show a new layer on a given action. When I perfom the action i get a javascript error, Cannot read property 'addClass' of null.  This action works fine without the trigger to show the layer. 

Here is the error;

player_compiled.js:563 Uncaught TypeError: Cannot read property 'addClass' of null
at Layer.show (player_compiled.js:563)
at TimelineAction.show_slidelayer (player_compiled.js:1061)
at Slide.Element.runAction (player_compiled.js:264)
at Slide.Element.runAction (player_compiled.js:265)
at TimelineAction.performAction (player_compiled.js:1058)
at TimelineAction.<anonymous> (player_compiled.js:1074)
at Function.each (player_compiled.js:21)
at StoryEvent.triggerEvent (player_compiled.js:1074)
at StoryEvent.<anonymous> (player_compiled.js:262)
at Function.each (player_compiled.js:21)

 

Line 563 contains;

this.ref.addClass("currentlayer");

 

Any assistance would be helpful.

Thanks

​