[media] gspca_gl860: Add a present check to sd_stop0

The sensor specific dev_post_unset_alt functions all try to write to the
bridge, and none free any memory, so they should be skipped if stop0
is called on disconnection.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/gspca/gl860/gl860.c

@@ -405,6 +405,9 @@ static void sd_stop0(struct gspca_dev *gspca_dev)
 {
 	struct sd *sd = (struct sd *) gspca_dev;
 
+	if (!sd->gspca_dev.present)
+		return;
+
 	return sd->dev_post_unset_alt(gspca_dev);
 }