message: Reflect empty string
  MarkedString::value is a mandatory field and the client may complain if `value` does not exist.
diff: @@ -67,8 +67,6 @@ void Reflect(Writer& visitor, std::string& value) {
  // ReflectMember
  void ReflectMember(Writer& visitor, const char* name, std::string& value) {
  - if (value.empty())
  - return;
  visitor.Key(name);
  Reflect(visitor, value);
  }
  