message: Delay creation of robots element until it is needed
diff: @@ -62,8 +62,6 @@ namespace
  if (structure->isRobotCommand())
  {
  - auto* robotsElement = new NAS2D::Xml::XmlElement("robots");
  -
  const auto& robots = static_cast<RobotCommand*>(structure)->robots();
  std::stringstream str;
  @@ -73,6 +71,7 @@ namespace
  if (i != robots.size() - 1) { str << ","; } // kind of a kludge
  }
  + auto* robotsElement = new NAS2D::Xml::XmlElement("robots");
  robotsElement->attribute("robots", str.str());
  structureElement->linkEndChild(robotsElement);
  }
  