in src/tree.rs [547:556]
fn build_merkle_tree_zero_padding(&mut self, list: &[P]) {
let tree_list: Vec<(TreeIndex, P)> = list
.iter()
.enumerate()
.map(|(index, p)| (tree_index_from_u64(self.height, index as u64), p.clone()))
.collect();
if let Some(x) = self.construct_smt_nodes(&tree_list, &ALL_ZEROS_SECRET) {
panic!("{}", x);
}
}