xdg-shell: Add invalid_parent error to xdg_popup

Send an invalid_parent error when the client tries to create a popup
with a paren that is neither a xdg_surface nor a xdg_popup.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
2 files changed