block: Fail blk_integrity_rq() gracefully.

Fail integrity check gracefully when request does not have a bio
attached.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

---

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -985,6 +985,9 @@ static inline int bdev_integrity_enabled
 
 static inline int blk_integrity_rq(struct request *rq)
 {
+	if (rq->bio == NULL)
+		return 0;
+
 	return bio_integrity(rq->bio);
 }