fdo#80280 Don't add items with no bitmaps

(cherry picked from commit cf26921658c0905a4d2dda13f91e3db99c76ade6)

Conflicts:
	cui/source/customize/cfg.cxx

Change-Id: I625aff5d2dcae0b1491fa77b04605d4579ec8530
Reviewed-on: https://gerrit.libreoffice.org/13068
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>