bcachefs: correctly initialize bch_extent_ptr

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/alloc_foreground.c

@@ -289,6 +289,7 @@ struct open_bucket *bch2_bucket_alloc(struct bch_fs *c, struct bch_dev *ca,
 	ob->valid	= true;
 	ob->sectors_free = ca->mi.bucket_size;
 	ob->ptr		= (struct bch_extent_ptr) {
+		.type	= 1 << BCH_EXTENT_ENTRY_ptr,
 		.gen	= buckets->b[bucket].mark.gen,
 		.offset	= bucket_to_sector(ca, bucket),
 		.dev	= ca->dev_idx,