message: Combine error checks in StructureManager::removeStructure
  Technically this is an updated and improved error check. The original
  check only checked if the first collection was empty, not if it did not
  contain the desired item.
diff: @@ -246,11 +246,6 @@ void StructureManager::removeStructure(Structure* structure)
  {
  StructureList& structures = mStructureLists[structure->structureClass()];
  - if (structures.empty())
  - {
  - throw std::runtime_error("StructureManager::removeStructure(): Attempting to remove a Structure that is not managed by the StructureManager.");
  - }
  -
  const auto it = std::find(structures.begin(), structures.end(), structure);
  if (it != structures.end())
  {
  @@ -263,7 +258,8 @@ void StructureManager::removeStructure(Structure* structure)
  tileTableIt->second->deleteThing();
  mStructureTileTable.erase(tileTableIt);
  }
  - else
  +
  + if ((it == structures.end()) || (tileTableIt == mStructureTileTable.end()))
  {
  throw std::runtime_error("StructureManager::removeStructure(): Attempting to remove a Structure that is not managed by the StructureManager.");
  }
  