
The intention of commit 4dc20398
was to disable unredirection while
banners are shown, but the ::done-displaying signal currently used for
re-enabling unredirection is only emitted under some circumstances, so
it's possible that unredirection is left disabled indefinitely, whoops.
Fix this by tying disabling unredirection explicitly to the lifetime
of the banner actor.
https://gitlab.gnome.org/GNOME/gnome-shell/issues/799