message: Use IOHelper's readResources in loadResorucesFromXmlElement
  The main difference is that IOHelper's `readResources` throws an
  exception if passed a `nullptr`, whereas `loadResorucesFromXmlElement`
  will silently do nothing.
diff: @@ -50,10 +50,7 @@ static void loadResorucesFromXmlElement(NAS2D::Xml::XmlElement* element, Storabl
  {
  if (!element) { return; }
  - resources.resources[0] = std::stoi(element->attribute(constants::SaveGameResource0));
  - resources.resources[1] = std::stoi(element->attribute(constants::SaveGameResource1));
  - resources.resources[2] = std::stoi(element->attribute(constants::SaveGameResource2));
  - resources.resources[3] = std::stoi(element->attribute(constants::SaveGameResource3));
  + resources = readResources(element);
  }
  