media: pci: cx23885: fix error handling for cx23885 ATSC boards

After having been assigned to NULL value at cx23885-dvb.c:1202,
pointer '0' is dereferenced at cx23885-dvb.c:2469.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Nikolay Burykin <burikin@ivk.ru>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>