mailbox_list_get_unexpanded_path(): Don't crash if namespace location is already expanded.
mailbox_list_get_unexpanded_path(): Don't crash if namespace location is already expanded.

--HG--
branch : HEAD

jwm/dovecot-notmuch,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot