quicklaunch.c: check return value of mkdir.
quicklaunch.c: check return value of mkdir.

This fixes coverity CID 1040044 Unchecked return value from library (CHECKED_RETURN).

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