message: invalidate domain when calling unknown known function to avoid false positives
diff: @@ -751,8 +751,10 @@ void FnCall::print(ostream &os) const {
  }
  StateValue FnCall::toSMT(State &s) const {
  - if (!valid)
  + if (!valid) {
  + s.addUB({});
  return {};
  + }
  // TODO: add support for memory
  // TODO: add support for global variables
  