Linter: fix list warning

lib/ui/gallery_app_bar_widget.dart

@@ -102,7 +102,7 @@ class _GalleryAppBarWidgetState extends State<GalleryAppBarWidget> {
   }
 
   List<Widget> _getDefaultActions(BuildContext context) {
-    List<Widget> actions = List<Widget>();
+    List<Widget> actions = <Widget>[];
     if (Configuration.instance.hasConfiguredAccount() &&
         (widget.type == GalleryAppBarType.local_folder ||
             widget.type == GalleryAppBarType.collection)) {
@@ -164,7 +164,7 @@ class _GalleryAppBarWidgetState extends State<GalleryAppBarWidget> {
   }
 
   List<Widget> _getActions(BuildContext context) {
-    List<Widget> actions = List<Widget>();
+    List<Widget> actions = <Widget>[];
     if (Configuration.instance.hasConfiguredAccount()) {
       actions.add(IconButton(
         icon:
@@ -270,7 +270,7 @@ class _GalleryAppBarWidgetState extends State<GalleryAppBarWidget> {
         containsLocalFile = true;
       }
     }
-    final actions = List<Widget>();
+    final actions = <Widget>[];
     if (containsUploadedFile && containsLocalFile) {
       actions.add(CupertinoActionSheetAction(
         child: Text("this device"),

lib/ui/location_search_results_page.dart

@@ -56,7 +56,7 @@ class _LocationSearchResultsPageState extends State<LocationSearchResultsPage> {
   static List<File> _filterPhotos(Map<String, dynamic> args) {
     List<File> files = args['files'];
     ViewPort viewPort = args['viewPort'];
-    final result = List<File>();
+    final result = <File>[];
     for (final file in files) {
       if (file.location != null &&
           viewPort.northEast.latitude > file.location.latitude &&

lib/ui/shared_collections_gallery.dart

@@ -279,7 +279,7 @@ class OutgoingCollectionItem extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final sharees = List<String>();
+    final sharees = <String>[];
     for (int index = 0; index < c.collection.sharees.length; index++) {
       if (index < 2) {
         sharees.add(c.collection.sharees[index].name);

lib/utils/diff_fetcher.dart

@@ -33,7 +33,7 @@ class DiffFetcher {
         )
         .catchError((e) => _logger.severe(e))
         .then((response) async {
-          final files = List<File>();
+          final files = <File>[];
           if (response != null) {
             Bus.instance.fire(RemoteSyncEvent(true));
             final diff = response.data["diff"] as List;
@@ -94,7 +94,7 @@ class DiffFetcher {
             return Diff(files, diff.length);
           } else {
             Bus.instance.fire(RemoteSyncEvent(false));
-            return Diff(List<File>(), 0);
+            return Diff(<File>[], 0);
           }
         });
   }