Otherwise the user object could outlive the dialogue, emit a subsequent
signal, and the callback from that signal could reference finalised
objects/widgets from the dialogue. The likely mechanism for the user
outliving the dialogue is caching of user objects within
libaccountsservice.
This can be triggered by running `pkexec true` from a gnome-terminal
window, then calling `pkill pkexec` from another terminal (on a
different VT or via SSH). This causes the dialogue to be cancelled by
polkitd.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/357