if (position != null) {
Field field = quadMap.getFieldAtPosition(position);
if (field != null) {
GameDataAccessor gameData = quadMap.getGameData();
CityReader cityReader = gameData.getCityReader();
if (cityReader.isCityIDAvailable(field.getPosition())
&& cityReader.getCityID(field.getPosition()) != null) {
Messages messages = Messages.getMessages();
messages.info("ConstructTestCityAction", "CityAR",
"You can't build more than one city on a field!");