refactor(hamt): remove child interface from hamt package

Author: overbool

hamt/hamt.go

@@ -362,7 +362,7 @@ func (ds *Shard) insertChild(idx int, key string, lnk *ipld.Link) error {
 	}
 
 	ds.children = append(ds.children[:i], append([]child{sv}, ds.children[i:]...)...)
-	ds.nd.SetLinks(append(ds.nd.Links()[:i], append([]*ipld.Link{nil}, ds.nd.Links()[i:]...)...))
+	ds.nd.SetLinks(append(ds.nd.Links()[:i], append([]*ipld.Link{lnk}, ds.nd.Links()[i:]...)...))
 	return nil
 }