Mms: fix Manage Sim Messages crash

- only set the item title if the menu item exists

Change-Id: If474de824121a3b376c3dbe1a1f48c3645ed01a3
Signed-off-by: Roman Birg <roman@cyngn.com>
(cherry picked from commit ac994034e874049a3508c5398202c5de9996aeff)