plasma-workspace: Backport recommendation to fix potential crash when closing Plasma popup

[Fusion Future]

Dear distro maintainers:

This patch fixes a potential crash when user closes a Plasma popup on 
Wayland. Please consider backporting the patch to plasma-workspace 
5.27.7. Thank you.

https://invent.kde.org/plasma/plasma-workspace/-/commit/fc01a7f837d06ee9e92d02f13acb79c2b06e9e3c

which fixes https://bugs.kde.org/show_bug.cgi?id=473054