Mark previewIDs as not nullable

mobile/lib/services/filedata/filedata_service.dart

@@ -23,7 +23,7 @@ class FileDataService {
   final _logger = Logger("FileDataService");
   final _dio = NetworkClient.instance.enteDio;
   late final SharedPreferences _prefs;
-  Map<int, PreviewInfo>? previewIds;
+  Map<int, PreviewInfo> previewIds = {};
 
   void init(SharedPreferences prefs) {
     _prefs = prefs;
@@ -33,9 +33,8 @@ class FileDataService {
   /// upload is successful, instead update the local copy of those
   /// preview ids
   void appendPreview(int id, String objectId, int objectSize) {
-    if (previewIds?.containsKey(id) ?? false) return;
-    previewIds ??= {};
-    previewIds?[id] = PreviewInfo(
+    if (previewIds.containsKey(id)) return;
+    previewIds[id] = PreviewInfo(
       objectId: objectId,
       objectSize: objectSize,
     );

mobile/lib/services/preview_video_store.dart

@@ -106,8 +106,7 @@ class PreviewVideoStore {
   Future<bool> isSharedFileStreamble(EnteFile file) async {
     try {
       if (FileDataService.instance.previewIds
-              ?.containsKey(file.uploadedFileID) ??
-          false) {
+          .containsKey(file.uploadedFileID)) {
         return true;
       }
       await _getPreviewUrl(file);
@@ -527,7 +526,7 @@ class PreviewVideoStore {
     try {
       late final String objectID;
       final PreviewInfo? previewInfo =
-          FileDataService.instance.previewIds?[file.uploadedFileID!];
+          FileDataService.instance.previewIds[file.uploadedFileID!];
       bool shouldAppendPreview = false;
       (String, String)? previewURLResult;
       if (previewInfo == null) {
@@ -768,7 +767,7 @@ class PreviewVideoStore {
 
     final previewIds = FileDataService.instance.previewIds;
     final allFiles = files
-        .where((file) => previewIds?[file.uploadedFileID] == null)
+        .where((file) => previewIds[file.uploadedFileID] == null)
         .sorted((a, b) {
       // put higher duration videos last along with remote files
       final first = (a.localID == null ? 2 : 0) +

mobile/lib/ui/viewer/file/file_details_widget.dart

@@ -180,8 +180,7 @@ class _FileDetailsWidgetState extends State<FileDetailsWidget> {
       const FileDetailsDivider(),
       if (widget.file.uploadedFileID != null &&
           (FileDataService.instance.previewIds
-                  ?.containsKey(widget.file.uploadedFileID) ??
-              false)) ...[
+              .containsKey(widget.file.uploadedFileID))) ...[
         ValueListenableBuilder(
           valueListenable: _exifNotifier,
           builder: (context, _, __) => PreviewPropertiesItemWidget(

mobile/lib/ui/viewer/file/video_stream_change.dart

@@ -38,8 +38,7 @@ class _VideoStreamChangeWidgetState extends State<VideoStreamChangeWidget> {
   Widget build(BuildContext context) {
     final bool isPreviewAvailable = widget.file.uploadedFileID != null &&
         (FileDataService.instance.previewIds
-                ?.containsKey(widget.file.uploadedFileID) ??
-            false);
+            .containsKey(widget.file.uploadedFileID));
     if (!isPreviewAvailable) {
       return const SizedBox();
     }

mobile/lib/ui/viewer/file/video_widget.dart

@@ -59,8 +59,7 @@ class _VideoWidgetState extends State<VideoWidget> {
     });
     if (widget.file.isUploaded) {
       isPreviewLoadable = FileDataService.instance.previewIds
-              ?.containsKey(widget.file.uploadedFileID) ??
-          false;
+          .containsKey(widget.file.uploadedFileID);
       if (!widget.file.isOwner) {
         // For shared video, we need to on-demand check if the file is streamable
         // and if not, we need to set isPreviewLoadable to false