message: more solid add_level_to_world()
diff: @@ -1946,12 +1946,17 @@ PyObject *py_unreal_engine_add_level_to_world(PyObject *self, PyObject * args)
  return PyErr_Format(PyExc_Exception, "argument is not a UWorld");
  }
  + if (!FPackageName::DoesPackageExist(UTF8_TO_TCHAR(name), nullptr, nullptr))
  + return PyErr_Format(PyExc_Exception, "package does not exist");
  +
  UClass *streaming_mode_class = ULevelStreamingKismet::StaticClass();
  if (py_bool && PyObject_IsTrue(py_bool))
  {
  streaming_mode_class = ULevelStreamingAlwaysLoaded::StaticClass();
  }
  +
  +
  #if ENGINE_MINOR_VERSION >= 17
  ULevelStreaming *level_streaming = EditorLevelUtils::AddLevelToWorld(u_world, UTF8_TO_TCHAR(name), streaming_mode_class);
  #else
  