resolve CastErrors

lib/ui/home/memories_widget.dart

@@ -410,9 +410,11 @@ class _FullScreenMemoryState extends State<FullScreenMemory> {
       extents: 1,
       onPageChanged: (index) async {
         await MemoriesService.instance.markMemoryAsSeen(widget.memories[index]);
-        setState(() {
-          _index = index;
-        });
+        if (mounted) {
+          setState(() {
+            _index = index;
+          });
+        }
       },
       physics: _shouldDisableScroll
           ? const NeverScrollableScrollPhysics()

lib/ui/viewer/file/file_info_widget.dart

@@ -51,9 +51,11 @@ class _FileInfoWidgetState extends State<FileInfoWidget> {
         widget.file.fileType == FileType.livePhoto;
     if (_isImage) {
       getExif(widget.file).then((exif) {
-        setState(() {
-          _exif = exif;
-        });
+        if (mounted) {
+          setState(() {
+            _exif = exif;
+          });
+        }
       });
     }
     super.initState();

lib/ui/viewer/file/video_widget.dart

@@ -78,7 +78,9 @@ class _VideoWidgetState extends State<VideoWidget> {
           .getFileSize(widget.file.uploadedFileID)
           .then((value) {
         widget.file.fileSize = value;
-        setState(() {});
+        if (mounted) {
+          setState(() {});
+        }
       });
     }
   }