message: add unwrap to dom/domtree.rs
diff: @@ -555,7 +555,7 @@ mod test {
  let mut dom = DomTree::build_dom_tree(&mut g, a);
  dom.compute_dominance_frontier();
  - let res = dom.dom_frontier(f);
  + let res = dom.dom_frontier(f).unwrap();
  let mut dom_front_f = HashSet::new();
  dom_front_f.insert(_g);
  @@ -564,7 +564,7 @@ mod test {
  assert_eq!(*i.0, i.1);
  }
  - let res = dom.dom_frontier(d);
  + let res = dom.dom_frontier(d).unwrap();
  let mut dom_front_d = HashSet::new();
  dom_front_d.insert(e);
  