This regressed in commit 12d904a71c
which changed the order of the pass to get the lower_popup pass before
the first inlining pass.
If by chance (which is likely if one have children), the component that
inherits from PopupWindow was inlined in that pass, it would be as
if it was not a component, and it would be removed from its parent.
But since it is no longer inlined, we need to support that case and
delay the removal when processing the component that holds that popup.
af1aa2991e