fix(mobile): clear album description sends null instead of empty string (#28817)

mobile/lib/domain/services/remote_album.service.dart

@@ -8,6 +8,7 @@ import 'package:immich_mobile/domain/models/user.model.dart';
 import 'package:immich_mobile/infrastructure/repositories/remote_album.repository.dart';
 import 'package:immich_mobile/models/albums/album_search.model.dart';
 import 'package:immich_mobile/providers/album/album_sort_by_options.provider.dart';
+import 'package:openapi/api.dart' show Optional;
 import 'package:immich_mobile/repositories/drift_album_api_repository.dart';
 import 'package:immich_mobile/services/foreground_upload.service.dart';
 import 'package:logging/logging.dart';
@@ -137,7 +138,7 @@ class RemoteAlbumService {
   Future<RemoteAlbum> updateAlbum(
     String albumId, {
     String? name,
-    String? description,
+    Optional<String?> description = const Optional.absent(),
     String? thumbnailAssetId,
     bool? isActivityEnabled,
     AlbumAssetOrder? order,

mobile/lib/presentation/pages/drift_remote_album.page.dart

@@ -20,6 +20,7 @@ import 'package:immich_mobile/providers/user.provider.dart';
 import 'package:immich_mobile/routing/router.dart';
 import 'package:immich_mobile/widgets/common/immich_toast.dart';
 import 'package:immich_mobile/widgets/common/remote_album_sliver_app_bar.dart';
+import 'package:openapi/api.dart' show Optional;
 
 @RoutePage()
 class RemoteAlbumPage extends ConsumerStatefulWidget {
@@ -247,10 +248,13 @@ class _EditAlbumDialogState extends ConsumerState<_EditAlbumDialog> {
     try {
       final newTitle = titleController.text.trim();
       final newDescription = descriptionController.text.trim();
+      final description = newDescription.isEmpty
+          ? const Optional<String?>.present(null)
+          : Optional<String?>.present(newDescription);
 
       await ref
           .read(remoteAlbumProvider.notifier)
-          .updateAlbum(widget.album.id, name: newTitle, description: newDescription);
+          .updateAlbum(widget.album.id, name: newTitle, description: description);
 
       if (mounted) {
         Navigator.of(

mobile/lib/providers/infrastructure/remote_album.provider.dart

@@ -8,6 +8,7 @@ import 'package:immich_mobile/domain/models/user.model.dart';
 import 'package:immich_mobile/domain/services/remote_album.service.dart';
 import 'package:immich_mobile/models/albums/album_search.model.dart';
 import 'package:immich_mobile/providers/album/album_sort_by_options.provider.dart';
+import 'package:openapi/api.dart' show Optional;
 import 'package:immich_mobile/providers/album/pending_album_uploads.provider.dart';
 import 'package:immich_mobile/providers/backup/asset_upload_progress.provider.dart';
 import 'package:immich_mobile/providers/infrastructure/album.provider.dart';
@@ -153,7 +154,7 @@ class RemoteAlbumNotifier extends Notifier<RemoteAlbumState> {
   Future<RemoteAlbum?> updateAlbum(
     String albumId, {
     String? name,
-    String? description,
+    Optional<String?> description = const Optional.absent(),
     String? thumbnailAssetId,
     bool? isActivityEnabled,
     AlbumAssetOrder? order,

mobile/lib/repositories/drift_album_api_repository.dart

@@ -71,7 +71,7 @@ class DriftAlbumApiRepository extends ApiRepository {
     String albumId,
     UserDto owner, {
     String? name,
-    String? description,
+    Optional<String?> description = const Optional.absent(),
     String? thumbnailAssetId,
     bool? isActivityEnabled,
     AlbumAssetOrder? order,
@@ -86,7 +86,7 @@ class DriftAlbumApiRepository extends ApiRepository {
         albumId,
         UpdateAlbumDto(
           albumName: name == null ? const Optional.absent() : Optional.present(name),
-          description: description == null ? const Optional.absent() : Optional.present(description),
+          description: description,
           albumThumbnailAssetId: thumbnailAssetId == null
               ? const Optional.absent()
               : Optional.present(thumbnailAssetId),