scsi: core: scsi_logging: Fix a BUG

The request_queue may be NULL in a request, for example when it comes from
scsi_ioctl_reset(). Check it before use.

Fixes: f3fa33acca9f ("block: remove the ->rq_disk field in struct request")
Link: https://lore.kernel.org/r/[e-mail]
Reported-by: Changhui Zhong <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Tomas Henzl <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/scsi_logging.c

···
 {
 	struct request *rq = scsi_cmd_to_rq((struct scsi_cmnd *)scmd);
 
-	if (!rq->q->disk)
+	if (!rq->q || !rq->q->disk)
 		return NULL;
 	return rq->q->disk->disk_name;
 }