regression from
	commit 7469e078
	loplugin:useuniqueptr in FmXGridCell

Change-Id: Ia74fcb518fe568d702101ff088f30dc8c096528f
Reviewed-on: https://gerrit.libreoffice.org/62346
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>