fix stack handling

mobile/lib/providers/asset_viewer/asset_stack.provider.dart

@@ -7,49 +7,49 @@ import 'package:riverpod_annotation/riverpod_annotation.dart';
 part 'asset_stack.provider.g.dart';
 
 class AssetStackNotifier extends StateNotifier<List<Asset>> {
-  final Asset _asset;
+  final String _stackId;
   final Ref _ref;
 
-  AssetStackNotifier(
-    this._asset,
-    this._ref,
-  ) : super([]) {
-    fetchStackChildren();
+  AssetStackNotifier(this._stackId, this._ref) : super([]) {
+    _fetchStack(_stackId);
   }
 
-  void fetchStackChildren() async {
-    if (mounted) {
-      state = await _ref.read(assetStackProvider(_asset).future);
+  void _fetchStack(String stackId) async {
+    if (!mounted) {
+      return;
+    }
+
+    final stack = await _ref.read(assetStackProvider(stackId).future);
+    if (stack.isNotEmpty) {
+      state = stack;
     }
   }
 
   void removeChild(int index) {
     if (index < state.length) {
       state.removeAt(index);
+      state = List<Asset>.from(state);
     }
   }
 }
 
 final assetStackStateProvider = StateNotifierProvider.autoDispose
-    .family<AssetStackNotifier, List<Asset>, Asset>(
-  (ref, asset) => AssetStackNotifier(asset, ref),
+    .family<AssetStackNotifier, List<Asset>, String>(
+  (ref, stackId) => AssetStackNotifier(stackId, ref),
 );
 
 final assetStackProvider =
-    FutureProvider.autoDispose.family<List<Asset>, Asset>((ref, asset) async {
-  // Guard [local asset]
-  if (asset.remoteId == null) {
-    return [];
-  }
-
-  return await ref
+    FutureProvider.autoDispose.family<List<Asset>, String>((ref, stackId) {
+  return ref
       .watch(dbProvider)
       .assets
       .filter()
       .isArchivedEqualTo(false)
       .isTrashedEqualTo(false)
-      .stackPrimaryAssetIdEqualTo(asset.remoteId)
-      .sortByFileCreatedAtDesc()
+      .stackIdEqualTo(stackId)
+      // orders primary asset first as its ID is null
+      .sortByStackPrimaryAssetId()
+      .thenByFileCreatedAtDesc()
       .findAll();
 });