V4L/DVB (8750): V4L: check inval in video_register_device_index()

Better check the video_device pointer before using it.

Signed-off-by: Henrik Kretzschmar <henne@nachtwindheim.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
index 6b9f3cb..8903e41 100644
--- a/drivers/media/video/v4l2-dev.c
+++ b/drivers/media/video/v4l2-dev.c
@@ -257,6 +257,9 @@
 	if (vfd == NULL)
 		return -EINVAL;
 
+	if (vfd == NULL)
+		return -EINVAL;
+
 	switch (type) {
 	case VFL_TYPE_GRABBER:
 		base = MINOR_VFL_TYPE_GRABBER_MIN;