message: fix spurious assertion crash
diff: @@ -1489,7 +1489,7 @@ static expr eq_except_padding(const Type &ty, const expr &e1, const expr &e2) {
  static expr not_poison_except_padding(const Type &ty, const expr &np) {
  const auto *aty = ty.getAsAggregateType();
  if (!aty) {
  - assert(np.isBool() && "non-aggregates should have boolean poison");
  + assert(!np.isValid() || np.isBool());
  return np;
  }
  