IndexOutOfBoundsException about stickyheaders HOT 6 CLOSED

public class AddressBookDemoActivity extends DemoActivity implements RandomUserLoader.OnLoadCallback {

    private static final String TAG = AddressBookDemoActivity.class.getSimpleName();
    AddressBookDemoAdapter adapter = new AddressBookDemoAdapter();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        recyclerView.setLayoutManager(new StickyHeaderLayoutManager());
        recyclerView.setAdapter(adapter);
    }

    @Override
    protected void onResume() {
        super.onResume();

        getRandomUserLoader().load(this);
    }

    @Override
    public void onRandomUsersDidLoad(List<Person> randomUsers) {

        recyclerView.post(() -> adapter.setPeople(randomUsers));
    }

    @Override
    public void onRandomUserLoadFailure(final Throwable t) {

        Snackbar snackbar = Snackbar.make(recyclerView, "Unable to load addressbook", Snackbar.LENGTH_LONG);
        snackbar.setAction(R.string.demo_addressbook_load_error_action, v -> showRandomUserLoadError(t.getLocalizedMessage()));
        snackbar.show();
    }

    private void showRandomUserLoadError(String message) {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle(R.string.demo_addressbook_load_error_dialog_title)
                .setMessage(message)
                .setPositiveButton(android.R.string.ok, null)
                .show();
    }

    private RandomUserLoader getRandomUserLoader() {
        return ((StickyHeadersDemoApp) getApplicationContext()).getRandomUserLoader();
    }
}