Disables the area tab when a line is selected

Change-Id: Ib02a68fb548a7cc10f9af7e0d1b6191119f18915
Reviewed-on: https://gerrit.libreoffice.org/16165Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>