m_aColumnWidths already contains it

Change-Id: I404c58fb0b32db7b7b7bf60be997f81709908ceb
Reviewed-on: https://gerrit.libreoffice.org/556Reviewed-by: Miklos Vajna <vmiklos@suse.cz>
Tested-by: Miklos Vajna <vmiklos@suse.cz>