getNotifications method Null safety

Implementation

Future<BuiltList<Notification>> getNotifications({
  final Instant? fromDate,
  final Instant? endDate,
  final bool? isRead,
  final String? inCategory,
  final String? withName,
  final int offset = 0,
  final int limit = 100,
}) async {
  final filters = <String>[
    if (fromDate != null)
      'dateTime_gte: "${InstantPattern.general.format(fromDate)}"',
    if (endDate != null)
      'dateTime_lte: "${InstantPattern.general.format(endDate)}"',
    if (isRead != null) 'read: ${isRead ? "true" : "false"}',
    if (inCategory != null) 'category: "$inCategory"',
    if (withName != null) 'withName: "$withName"',
  ];

  final gqlQueryString = '''
    query FetchNotifications {
      notifications(sort: "dateTime:desc", start: $offset, limit: $limit, where: { ${filters.join(",")} }) {
        ${NotificationGqlEntity.gqlQueryFragment}
      }
    }
  ''';

  try {
    final queryResult = await graphQLClient.query<void>(QueryOptions(
        document: gql(gqlQueryString), fetchPolicy: FetchPolicy.networkOnly));

    if (queryResult.hasException) {
      logger?.e(queryResult.exception.toString());
      return BuiltList<Notification>();
    }

    final data = queryResult.data!['notifications'] as List<dynamic>;
    final l = data
        .map((dynamic e) =>
            NotificationGqlEntity.fromJson(e as Map<String, dynamic>))
        .where((element) => element != null)
        .map((element) => element!.toNotification())
        .toBuiltList();

    if (!_notificationStreamController.isClosed) {
      _notificationStreamController.add(l);
    }

    return l;
  } catch (e, stackTrace) {
    logger?.e('Could not read notifications', e.toString(), stackTrace);
    return BuiltList<Notification>();
  }
}