Don't remove SettingsListItem content from tree (#259)

* Don't remove SettingsListItem content from tree

* Remove unused variable

gallery/gallery/lib/pages/settings_list_item.dart

@@ -185,7 +185,6 @@ class _SettingsListItemState<T> extends State<SettingsListItem<T>>
   @override
   Widget build(BuildContext context) {
     _handleExpansion();
-    final closed = !widget.isExpanded && _controller.isDismissed;
     final theme = Theme.of(context);
 
     final optionsList = <Widget>[];
@@ -227,9 +226,7 @@ class _SettingsListItemState<T> extends State<SettingsListItem<T>>
     return AnimatedBuilder(
       animation: _controller.view,
       builder: _buildHeaderWithChildren,
-      child: closed
-          ? null
-          : Container(
+      child: Container(
         margin: const EdgeInsetsDirectional.only(start: 24, bottom: 40),
         decoration: BoxDecoration(
           border: BorderDirectional(