message: Move static_cast out of readRccRobots
  If the function is only meant to work on RobotCommand structures, then
  that's what it should accept. It would be unsafe to call it with any
  other type of Structure.
diff: @@ -54,7 +54,7 @@ static void loadResorucesFromXmlElement(NAS2D::Xml::XmlElement* element, Storabl
  }
  -static void readRccRobots(NAS2D::Xml::XmlAttribute* attr, Structure& structure, RobotPool& pool)
  +static void readRccRobots(NAS2D::Xml::XmlAttribute* attr, RobotCommand& robotCommand, RobotPool& pool)
  {
  if (!attr) { return; }
  @@ -65,7 +65,7 @@ static void readRccRobots(NAS2D::Xml::XmlAttribute* attr, Structure& structure,
  {
  if (robot->id() == robotId)
  {
  - static_cast<RobotCommand*>(&structure)->addRobot(robot);
  + robotCommand.addRobot(robot);
  break;
  }
  }
  @@ -501,7 +501,8 @@ void MapViewState::readStructures(Xml::XmlElement* element)
  auto robotsElement = structureElement->firstChildElement("robots");
  if (robotsElement)
  {
  - readRccRobots(robotsElement->firstAttribute(), structure, mRobotPool);
  + auto& robotCommand = *static_cast<RobotCommand*>(&structure);
  + readRccRobots(robotsElement->firstAttribute(), robotCommand, mRobotPool);
  }
  }
  