message: fix crash with phi nodes due to a dangling ref
diff: @@ -68,7 +68,7 @@ const State::ValTy& State::at(const Value &val) const {
  }
  const expr* State::jumpCondFrom(const BasicBlock &bb) const {
  - auto pres = predecessor_domain.at(current_bb);
  + auto &pres = predecessor_domain.at(current_bb);
  auto I = pres.find(&bb);
  return I == pres.end() ? nullptr : &I->second.first;
  }
  