Btrfs: remove BUG() in print_extent_item

btrfs_print_leaf() is used in btrfs_get_extent_inline_ref_type, so
here we really want to print the invalid value of ref type instead of
causing a kernel panic.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/print-tree.c

@@ -121,7 +121,10 @@ static void print_extent_item(struct extent_buffer *eb, int slot, int type)
 			       offset, btrfs_shared_data_ref_count(eb, sref));
 			break;
 		default:
-			BUG();
+			btrfs_err(eb->fs_info,
+				  "extent %llu has invalid ref type %d",
+				  eb->start, type);
+			return;
 		}
 		ptr += btrfs_extent_inline_ref_size(type);
 	}