block: add a sanity check for a live disk in del_gendisk

Add a sanity check to del_gendisk to do nothing when the disk wasn't
successfully added.  This papers over the complete lack of add_disk
error handling, which is about to get fixed gradually.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210818144542.19305-2-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/genhd.c

@@ -579,7 +579,7 @@ void del_gendisk(struct gendisk *disk)
 {
 	might_sleep();
 
-	if (WARN_ON_ONCE(!disk->queue))
+	if (WARN_ON_ONCE(!disk_live(disk)))
 		return;
 
 	blk_integrity_del(disk);