wl1251: fix NULL pointer dereference
Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Reported-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: John W. Linville <linville@tuxdriver.com>