SQFLite plugin com erro

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return BlocProvider<SettingsBloc>(
      bloc: SettingsBloc(),
      child: MaterialApp(
        theme: ThemeData(
          primarySwatch: Colors.red,
        ),
        title: APP_TITLE,
        debugShowCheckedModeBanner: false,
        home: SyncWrapper(),
      ),
    );
  }
}

class SyncWrapper extends StatefulWidget {
  @override
  _SyncWrapperState createState() => _SyncWrapperState();
}

class _SyncWrapperState extends State<SyncWrapper> {
  AbastecimentoHelper _abHelper;

  @override
  void initState() {
    super.initState();

    _abHelper = AbastecimentoHelper();

    _abHelper.syncPendentes();
  }

  @override
  Widget build(BuildContext context) {
    final bloc = BlocProvider.of<SettingsBloc>(context);
    return StreamBuilder<SettingsState>(
      stream: bloc.outState,
      builder: (context, snapshot) {
        if (snapshot.data != SettingsState.DONE) {
          return Center(
            child: CircularProgressIndicator(),
          );
        }

        return HomeScreen();
      },
    );
  }

  @override
  void dispose() {
    _abHelper.close();
    super.dispose();
  }
}

class AbastecimentoHelper {
  static final AbastecimentoHelper _instance = AbastecimentoHelper.internal();

  factory AbastecimentoHelper() => _instance;

  AbastecimentoHelper.internal();

  Database _db;

  Future<Database> get db async {
    if (_db != null) return _db;

    _db = await initDb();

    return _db;
  }

  Future<Database> initDb() async {
    final databasesPath = await getDatabasesPath();
    final path = join(databasesPath, 'maissync.db');

    return openDatabase(path, version: 1,
        onCreate: (Database db, int newerVersion) async {
      String schema = "CREATE TABLE $abastecimentoTable("
          "$stringColumn TEXT NOT NULL,"
          "$dataLeituraColumn TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL,"
          "$dataSincronizadoColumn TIMESTAMP DEFAULT NULL"
          ")";

      await db.execute(schema);
    });
  }

  Future close() async {
    Database dbAbastecimento = await db;
    dbAbastecimento.close();
  }

  Future<void> syncPendentes() async {
    List pendentes = await getPendentes();
    if (pendentes.length > 0) {
      try {
        String body = json.encode({"abastecimentos": pendentes});
        var response = await http.post(API_ENDPOINT_ABASTECIMENTOS, body: body);

        if (response.statusCode == 200) {
          List<int> ids = [];
          String whereStr = "";
          for (var p in pendentes) {
            ids.add(p["rowid"]);
            whereStr += "?, ";
          }
          whereStr = "(${whereStr.substring(0, whereStr.length - 2)})";

          Database dbAbastecimento = await db;
          await dbAbastecimento.update(
            abastecimentoTable,
            {"$dataSincronizadoColumn": nowStr()},
            where: "$rowIdColumn IN $whereStr",
            whereArgs: ids,
          );

        } else {
          debugLog(
            file: "helpers/abastecimento-helper.dart",
            method: "syncPendentes",
            location: "Falha na requisição",
            message: "Falha na requisição... Status: ${response.statusCode}.",
          );
        }
      } catch (e) {
        debugLog(
          file: "helpers/abastecimento-helper.dart",
          method: "syncPendentes",
          location: "Erro endpoint/desconhecido",
          message: "Falha desconhecida na requisição HTTP...\n"
              "\t\t- Provavelmente o Endpoint não está respondendo!",
        );
      }
    }

    // Interval
    Future.delayed(SQLITE_CHECK_INTERVAL).then((_) {
      syncPendentes();
    });
  }

  Future<List> getPendentes() async {
    Database dbAbastecimento = await db;

    List listMap = await dbAbastecimento.query(
      abastecimentoTable,
      columns: [rowIdColumn, stringColumn],
      where: "$dataSincronizadoColumn IS NULL",
      orderBy: "$rowIdColumn",
      limit: SYNC_ROWS,
    );

    return listMap;
  }

}