transit - fix the double free obj_data case.
transit - fix the double free obj_data case.

if the object is added twice to the one transit,
the obj_remove_cb would be called twice.

in this case it will try to access the freed obj_data and crashed up.

now it's fixed.

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