static Collection<Web> ai_withoutInvalidWebs(Collection<Web> l) {
  if (l == null) null;
  for (Web n : l)
    if (ai_isInvalidWeb(n)) {
      Iterator<Web> it = iterator(l);
      Web node;
      new L<Web> x;
      while ((node = it.next()) != n)
        x.add(node);
      while (it.hasNext()) {
        node = it.next();
        if (!ai_isInvalidWeb(node))
          x.add(node);
      }
      ret x;
    }
  ret l;
}

static L<Web> ai_withoutInvalidWebs(L<Web> l) {
  ret (L) ai_withoutInvalidWebs((Collection) l);
}

Began life as a copy of #1011427