addJusoStreamListener method Null safety

Implementation

addJusoStreamListener() {
  jusoVM.jusoResult.listen((list) {
    jusoVM.jusoList = list;
    setState(() {});
  }, onError: (error, stacktrace) {
    print("onError: $error");
    print(stacktrace.toString());

    if (error is ErrorModel == false) return;

    ErrorModel errorModel = error;
    if (jusoVM.page == 1) jusoVM.jusoList = [];
    if (errorModel.error == -101) jusoVM.page = -1;

    jusoVM.errorMessage = errorModel.message;
    setState(() {});
  });
}