`late _timer` was not initialized but used in widgets `dispose` method if [Line 51](https://github.com/tiny-express/flutter_scroll_gallery/blob/ab237225052d642b7dc4808b04ecd7d80f9297d4/lib/src/scroll_gallery.dart#L51) evaluated to false
late _timerwas not initialized but used in widgetsdisposemethod if Line 51 evaluated to false