VTK Chart Overlay Doesn't work with VTK 9

@codeling That makes sense. Glad you found the problem.

BTW I agree that it would be good with some kind of warning/error mechanism for when you enable some piece of functionality (e.g. RenderingContext2D), but there’s no implementation module for it (e.g. RenderingContextOpenGL2) enabled, since that’s sort of a non-sensical config.