Remove NULL pointer in stb6000 driver,
as it raises error for DvbWorld USB card.
Signed-off-by: Igor M. Liplianin <liplianin@me.by>
Signed-off-by: Steven Toth <stoth@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>