wayland/surface: Can't send scale events with NULL surface->resource
requested to merge daenzer/mutter:wayland-surface-committed_state_handle_highest_scale_monitor-NULL-resource into main
The committed state can't have any children sub-surfaces either, so just bail.
Fixes: ae403f2e ("wayland: Use new highest scale monitor tracking for fractional_scale_v1") Closes: #3552 (closed)