message: Return mouseTilePosition value by const&
diff: @@ -60,7 +60,7 @@ public:
  void moveView(Direction direction);
  bool tileHighlightVisible() const;
  - MapCoordinate mouseTilePosition() const { return mMouseTilePosition; }
  + const MapCoordinate& mouseTilePosition() const { return mMouseTilePosition; }
  const Point2dList& mineLocations() const { return mMineLocations; }
  void removeMineLocation(const NAS2D::Point<int>& pt);
  