message: Iterate over only XmlElement nodes for mine veins
diff: @@ -340,10 +340,10 @@ void Mine::deserialize(NAS2D::Xml::XmlElement* element)
  mProductionRate = static_cast<MineProductionRate>(yield);
  mVeins.resize(static_cast<std::size_t>(depth));
  - for (XmlNode* vein = element->firstChild(); vein != nullptr; vein = vein->nextSibling())
  + for (auto* vein = element->firstChildElement(); vein != nullptr; vein = vein->nextSiblingElement())
  {
  auto mineVein = MineVein{0, 0, 0, 0};
  - auto* attribute = vein->toElement()->firstAttribute();
  + auto* attribute = vein->firstAttribute();
  int id = 0;
  while (attribute)
  {
  