NullPointerException sometimes after download starting

[s681562]

D/FLUTTER OTA(14386): STREAM OPENED
D/FLUTTER OTA(14386): REQUEST PERMISSIONS RESULT RECEIVED
D/FLUTTER OTA(14386): DOWNLOAD STARTING
E/AndroidRuntime(14386): FATAL EXCEPTION: main
E/AndroidRuntime(14386): Process: kr.co.klcns.mrs_app, PID: 14386
E/AndroidRuntime(14386): java.lang.RuntimeException: Failure delivering result ResultInfo{who=@android:requestPermissions:, request=0, result=-1, data=Intent { act=android.content.pm.action.REQUEST_PERMISSIONS (has extras) }} to activity {kr.co.klcns.mrs_app/kr.co.klcns.mrs_app.MainActivity}: java.lang.NullPointerException
E/AndroidRuntime(14386): at android.app.ActivityThread.deliverResults(ActivityThread.java:5864)
E/AndroidRuntime(14386): at android.app.ActivityThread.handleSendResult(ActivityThread.java:5903)
E/AndroidRuntime(14386): at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:54)
E/AndroidRuntime(14386): at android.app.servertransaction.ActivityTransactionItem.execute(ActivityTransactionItem.java:45)
E/AndroidRuntime(14386): at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
E/AndroidRuntime(14386): at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
E/AndroidRuntime(14386): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2438)
E/AndroidRuntime(14386): at android.os.Handler.dispatchMessage(Handler.java:106)
E/AndroidRuntime(14386): at android.os.Looper.loopOnce(Looper.java:226)
E/AndroidRuntime(14386): at android.os.Looper.loop(Looper.java:313)
E/AndroidRuntime(14386): at android.app.ActivityThread.main(ActivityThread.java:8663)
E/AndroidRuntime(14386): at java.lang.reflect.Method.invoke(Native Method)
E/AndroidRuntime(14386): at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:571)
E/AndroidRuntime(14386): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1135)
E/AndroidRuntime(14386): Caused by: java.lang.NullPointerException
E/AndroidRuntime(14386): at k1.a.b(Unknown Source:38)
E/AndroidRuntime(14386): at io.flutter.embedding.engine.c$c.h(Unknown Source:20)
E/AndroidRuntime(14386): at io.flutter.embedding.engine.c.b(Unknown Source:14)
E/AndroidRuntime(14386): at io.flutter.embedding.android.d.y(Unknown Source:59)
E/AndroidRuntime(14386): at io.flutter.embedding.android.c.onRequestPermissionsResult(Unknown Source:10)
E/AndroidRuntime(14386): at android.app.Activity.dispatchRequestPermissionsResult(Activity.java:8833)
E/AndroidRuntime(14386): at android.app.Activity.dispatchActivityResult(Activity.java:8663)
E/AndroidRuntime(14386): at android.app.ActivityThread.deliverResults(ActivityThread.java:5857)
E/AndroidRuntime(14386): ... 13 more

Here my snippet:

`
void _onVersionUpdate(VersionUpdate event, Emitter emit) async {
SharedPreferences prefs = await SharedPreferences.getInstance();
String protocol = prefs.containsKey('protocol') ? prefs.getString('protocol')! : "https";
String host = prefs.containsKey('host') ? prefs.getString('host')! : "0.0.0.0";
int port = prefs.containsKey('port') ? prefs.getInt('port')! : 0;
String jwt = prefs.containsKey('token') ? prefs.getString('token')! : "";
PackageInfo packageInfo = await PackageInfo.fromPlatform();

try {
OtaUpdateVersion otaUpdateVersion = await HttpClientService().getVersion(protocol, host, port, jwt, packageInfo.version);
String path = otaUpdateVersion.path;
final String url = sprintf("%s://%s:%s/%s", [protocol, host, port, path]);

OtaUpdate().execute(url, headers: {'Accept': 'application/octet-stream'},).listen(
  (OtaEvent event) async {
    switch (event.status) {
      case OtaStatus.CANCELED:
        break;
      case OtaStatus.ALREADY_RUNNING_ERROR:
        break;
      case OtaStatus.CHECKSUM_ERROR:
        break;
      case OtaStatus.PERMISSION_NOT_GRANTED_ERROR:
        break;
      case OtaStatus.DOWNLOAD_ERROR:
        break;
      case OtaStatus.INTERNAL_ERROR:
        break;
      case OtaStatus.DOWNLOADING:
        try {
          try {
            add(LoginPageUpdateChanged(event: event, version: otaUpdateVersion.version));
          } on StateError catch (e) {
            FileLogger.write('Failed to make OTA update. Details: $e');
          }
        } on StateError catch (e) {
          FileLogger.write('Failed to make OTA update. Details: $e');
        }
        break;
      case OtaStatus.INSTALLING:
        try {
          add(LoginPageInitEvent());
        } on StateError catch (e) {
          FileLogger.write('Failed to make OTA update. Details: $e');
        }
        FileLogger.write("tryOtaUpdate: $event");
        break;
    }
  },
);

} catch (e) {
FileLogger.write('Failed to make OTA update. Details: $e');
}
}

`

How to catch this error? Sometimes unexpected happen. Any idea?