Dispose `_treeViewScrollController` (#1062)

desktop_photo_search/fluent_ui/lib/src/widgets/unsplash_search_content.dart

@@ -21,6 +21,12 @@ class UnsplashSearchContent extends StatefulWidget {
 class _UnsplashSearchContentState extends State<UnsplashSearchContent> {
   final _treeViewScrollController = ScrollController();
 
+  @override
+  dispose() {
+    _treeViewScrollController.dispose();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) {
     final photoSearchModel = Provider.of<PhotoSearchModel>(context);

desktop_photo_search/material/lib/src/widgets/unsplash_search_content.dart

@@ -22,6 +22,12 @@ class UnsplashSearchContent extends StatefulWidget {
 class _UnsplashSearchContentState extends State<UnsplashSearchContent> {
   final _treeViewScrollController = ScrollController();
 
+  @override
+  dispose() {
+    _treeViewScrollController.dispose();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) {
     final photoSearchModel = Provider.of<PhotoSearchModel>(context);