fdo#62815 - tolerate crazy / out-of-bound ScreenNumbers for FullScreen
Thus making the gtk+ backend more similar to the generic backend
in this regard; also be more strict about invalid monitors -> empty
screens.
Change-Id: Ia4f2e1205cb1d309fb1bb01f9631167339a3478e
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Reviewed-on: https://gerrit.libreoffice.org/3695
Reviewed-by: Fridrich Strba <fridrich@documentfoundation.org>
Tested-by: Caolán McNamara <caolanm@redhat.com>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>