message: Use isValidPosition to precheck getTile in MapViewState
diff: @@ -434,13 +434,10 @@ void MapViewState::onMouseDown(EventHandler::MouseButton button, int /*x*/, int
  }
  if (!mTileMap->tileHighlightVisible()) { return; }
  + if (!mTileMap->isValidPosition(mTileMap->tileMouseHover())) { return; }
  Tile* _t = mTileMap->getTile(mTileMap->tileMouseHover());
  - if (!_t)
  - {
  - return;
  - }
  - else if (_t->empty() && mTileMap->boundingBox().contains(MOUSE_COORDS))
  + if (_t->empty() && mTileMap->boundingBox().contains(MOUSE_COORDS))
  {
  clearSelections();
  mTileInspector.tile(_t);
  @@ -557,9 +554,10 @@ void MapViewState::onMouseDoubleClick(EventHandler::MouseButton button, int /*x*
  {
  if (mWindowStack.pointInWindow(MOUSE_COORDS)) { return; }
  if (!mTileMap->tileHighlightVisible()) { return; }
  + if (!mTileMap->isValidPosition(mTileMap->tileMouseHover())) { return; }
  Tile* _t = mTileMap->getTile(mTileMap->tileMouseHover());
  - if (_t && _t->thingIsStructure())
  + if (_t->thingIsStructure())
  {
  Structure* structure = _t->structure();
  