message: null pointer check for value in json serializer
diff: @@ -102,6 +102,11 @@ void Serializer::writeObject(oatpp::data::stream::OutputStream* stream, const Po
  void Serializer::writeValue(oatpp::data::stream::OutputStream* stream, const AbstractObjectWrapper& polymorph, const std::shared_ptr<Config>& config) {
  + if(!polymorph) {
  + stream->write("null", 4);
  + return;
  + }
  +
  const char* typeName = polymorph.valueType->name;
  if(typeName == oatpp::data::mapping::type::__class::String::CLASS_NAME) {
  