Action API: ArtboardChanged event oldArtboard always "<null>" in version 54
I call the action event ["ArtboardChanged"](https://developer.sketch.com/reference/action/ArtboardChanged/) to create a [Artboard History](https://github.com/jan-patrick/sketch_artboard-history). It worked perfectly with the previous released version but with version 54 there seems to be a bug with that event. It still gets called but the "oldArtboard" var is always "<null\>" and by that the event isn't working for me anymore:
`oldArtboard = "<null>";`