Backport !2147 “snap: Fix crash when uninstalling snap” to gnome-47
requested to merge pwithnall/gnome-software:backport-2147-snap-uninstall-app-crash-fix-gnome-47 into gnome-47
'app_data' is an argument to both the actual and progress
callbacks. In this case, using g_steal_pointer
on one of them will
render the other one to be NULL, causing the crash. Follow the same
convention used in install.
Trivial backport of !2147 (merged) to gnome-47
.