in pr https://github.com/swaywm/sway/pull/8196, when im_popup_surface is unmapped, author set the popup->relative to NULL, butt popup is still in popup groups, where assert the relative is not NULL, this cause the panic
Take the suggestion of Nefsen402, remove the line where set relative to
NULL, and add NULL check in scene_descriptor_destory
Across a wayland compositor, there are multiple shells: It can be
a toplevel, or a layer_shell, or even something more meta like a drag
icon or highlight indicators when dragging windows around.
This object lets us store values that represent these modes of operation
and keep track of what object is being represented.
