Fix close_popups for xdg-shell
Fix close_popups for xdg-shell

wlr_xdg_popup_destroy will destroy popups, so we need to walk the tree
carefully. It's enough to just destroy all direct children, since destroying
the parent will also destroy all children.

1ace/sway,ascent12/sway,SirCmpwn/sway,1ace/sway,ascent12/sway,ascent12/sway,1ace/sway