It is... I think it might be limited to the viewport actions or perhaps there was something specific about the state in the document that lead to this condition - I have more investigating to do.
Hah, I had been getting that of late , in particularlly when I copied a scene or symbol from one project to another. If it originally had an on scene/symbol load Run Javascript function and the function was not actually in the new project I get the error. Took me a while to figure it out.. thought I was going nuts because in some case I did not have any functions running. As soon as I removed the action. All worked..
I am sure this is a new bug.