Derive the chapter menu, or null when this scene has no chapter dimension.
null
null is a legitimate, common answer — most scenes are not tours — and the caller's job is to say so plainly rather than draw an empty grid.
Derive the chapter menu, or
nullwhen this scene has no chapter dimension.nullis a legitimate, common answer — most scenes are not tours — and the caller's job is to say so plainly rather than draw an empty grid.