btrfs: convert BUG() for pending_del_nr into an ASSERT

This is a logic correctness check, convert it into an ASSERT() instead
of a BUG().
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode-item.c

@@ -651,6 +651,9 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
 		else
 			control->last_size = new_size;
 		if (del_item) {
+			ASSERT(!pending_del_nr ||
+			       ((path->slots[0] + 1) == pending_del_slot));
+
 			if (!pending_del_nr) {
 				/* No pending yet, add ourselves */
 				pending_del_slot = path->slots[0];
@@ -660,8 +663,6 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
 				/* Hop on the pending chunk */
 				pending_del_nr++;
 				pending_del_slot = path->slots[0];
-			} else {
-				BUG();
 			}
 		} else {
 			break;