anchor.diff:            new IconButton(
               icon: new Icon(Icons.more_vert),
               tooltip: 'Show menu',
  -            onPressed: () { showConfigurationSheet(context); },
  +            onPressed: _bottomSheet == null ? _showConfigurationSheet : null,
             ),
           ],
         ),
  
positive.code:           ],
          ),
        );
      });
    }
  
  
negative.code:     _bottomSheet?.setState(() { });
    }
  
    void _showConfigurationSheet() {
      final PersistentBottomSheetController<Null> bottomSheet = scaffoldKey.currentState.showBottomSheet((BuildContext bottomSheetContext) {
        return new Container(
          decoration: new BoxDecoration(
            border: new Border(top: new BorderSide(color: Colors.black26)),
  