media: gspca: null check create_singlethread_workqueue

In sd_start the return value of create_singlethread_workqueue needs
null check.
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/usb/gspca/sq905c.c

@@ -276,6 +276,9 @@ static int sd_start(struct gspca_dev *gspca_dev)
 	}
 	/* Start the workqueue function to do the streaming */
 	dev->work_thread = create_singlethread_workqueue(MODULE_NAME);
+	if (!dev->work_thread)
+		return -ENOMEM;
+
 	queue_work(dev->work_thread, &dev->work_struct);
 
 	return 0;