fm: Check return of strrchr
fm: Check return of strrchr

strrchr can return NULL, so we need to check the return value.

CID 1039861

tasn/enlightenment,FlorentRevest/Enlightenment,tasn/enlightenment,tizenorg/platform.upstream.enlightenment,tizenorg/platform.upstream.enlightenment,tasn/enlightenment,rvandegrift/e,rvandegrift/e,rvandegrift/e,FlorentRevest/Enlightenment,tizenorg/platform.upstream.enlightenment,FlorentRevest/Enlightenment