Gengrid: fix segv in _elm_gengrid_item_edge_check.
Gengrid: fix segv in _elm_gengrid_item_edge_check.

Reviewers: raster, seoz

Reviewed By: raster

CC: seoz

Differential Revision: https://phab.enlightenment.org/D695

rvandegrift/elementary,rvandegrift/elementary,FlorentRevest/Elementary,FlorentRevest/Elementary,tasn/elementary,tasn/elementary,rvandegrift/elementary,FlorentRevest/Elementary,tasn/elementary,tasn/elementary,tasn/elementary,rvandegrift/elementary,FlorentRevest/Elementary