Currently, the password_entry_timeout() callback can be called even after
the dialog disposal, which leads to segfaults. This is because the
corresponding source ids can be cleared in some cases without removing
the sources. Let's prevent direct calls of password_entry_timeout()
without destroying the source ids in order to fix this issue.
Fixes: https://gitlab.gnome.org/GNOME/gnome-control-center/issues/760
If "Esc" is pressed, the callbacks to handle the `focus-out` signal are
called after the `cc_password_dialog_dispose` function. This leads to
segfaults, because the `user` variable is already cleared. Let's simply
do not continue if `user == NULL` to fix those crashes.
Closes: https://gitlab.gnome.org/GNOME/gnome-control-center/issues/563
