Flutter local notification doesn't work and gives me PlatformException

Question

I am trying to show notifications in my Flutter app but I am getting this exception:

Unhandled Exception: PlatformException(error, Attempt to invoke virtual method 'boolean java.lang.Boolean.booleanValue()' on a null object reference, null, java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.Boolean.booleanValue()' on a null object reference

this is the method I'm using. How can I fix it?

void sendNotification({String? title, String? body}) async {
  FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin =
  FlutterLocalNotificationsPlugin();

   const AndroidInitializationSettings initializationSettingsAndroid =
  AndroidInitializationSettings('@mipmap/ic_launcher');
  const IOSInitializationSettings initializationSettingsIOS =
  IOSInitializationSettings(
    requestAlertPermission: true,
    requestBadgePermission: true,
    requestSoundPermission: true,
  );

  const InitializationSettings initializationSettings = InitializationSettings(
      android: initializationSettingsAndroid,
      iOS: initializationSettingsIOS,);
  await flutterLocalNotificationsPlugin.initialize(
    initializationSettings,
  );

  flutterLocalNotificationsPlugin.show(
    0,
    title,
    body,
    const NotificationDetails(
      android:
          AndroidNotificationDetails(
              'channel id',
              'channel',
              'channel description',
              importance: Importance.max
          )),
    );

}