V4L/DVB (7891): cx18/ivtv: fix open() kernel oops

Upon error conditions in cx18/ivtv_probe(), the code at the 'err:' label
leaves a NULL entry in cx18/ivtv_cards[]. This can cause a NULL pointer
de-reference in cx18/ivtv_v4l2_open() which is fixed by this patch.

Signed-off-by: Andy Walls <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/video/cx18/cx18-fileops.c

···
 	for (x = 0; cx == NULL && x < cx18_cards_active; x++) {
 		/* find out which stream this open was on */
 		for (y = 0; y < CX18_MAX_STREAMS; y++) {
+			if (cx18_cards[x] == NULL)
+				continue;
 			s = &cx18_cards[x]->streams[y];
 			if (s->v4l2dev && s->v4l2dev->minor == minor) {
 				cx = cx18_cards[x];

drivers/media/video/ivtv/ivtv-fileops.c

···
 	/* Find which card this open was on */
 	spin_lock(&ivtv_cards_lock);
 	for (x = 0; itv == NULL && x < ivtv_cards_active; x++) {
+		if (ivtv_cards[x] == NULL)
+			continue;
 		/* find out which stream this open was on */
 		for (y = 0; y < IVTV_MAX_STREAMS; y++) {
 			s = &ivtv_cards[x]->streams[y];