Как я могу разрешить получение этого исключения с нулевым указателем при настройке видимости пункта меню?

Question

public class menulayout extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener , AdapterView.OnItemSelectedListener {

    DrawerLayout drawerLayout;
    NavigationView navigationView;
    ImageView menuIcon;
    Menu menu;
 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_menulayout);
        drawerLayout = findViewById(R.id.drawer_layout);
        navigationView = findViewById(R.id.nav_view);
        menuIcon = findViewById(R.id.menubutton);  
navigationView.bringToFront();
        ActionBarDrawerToggle toggle = new
                ActionBarDrawerToggle(this, drawerLayout, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawerLayout.addDrawerListener(toggle);
        toggle.syncState();
        navigationView.setNavigationItemSelectedListener(this);
        navigationView.setCheckedItem(R.id.home);

        menuIcon.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (drawerLayout.isDrawerVisible(GravityCompat.START)) {
                    drawerLayout.closeDrawer(GravityCompat.START);
                } else {
                    drawerLayout.openDrawer(GravityCompat.START);
                }
            }
        });
    }

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
        switch (menuItem.getItemId()) {
            case R.id.home:
                break;
            case R.id.tutorial:
                Intent intent = new Intent(menulayout.this, activity6.class);
            startActivity(intent);
            break;
            case R.id.log:
                intent = new Intent(menulayout.this, activity6.class);
                startActivity(intent);
                menu.findItem(R.id.out).setVisible(true);
                menu.findItem(R.id.details).setVisible(true);
                menu.findItem(R.id.log).setVisible(false);

                break;
            case R.id.out:
                menu.findItem(R.id.out).setVisible(false);
                menu.findItem(R.id.details).setVisible(false);
                menu.findItem(R.id.log).setVisible(true);
                break;
            case R.id.share:
                Toast.makeText(this, "Share", Toast.LENGTH_SHORT).show();
                break;
        }
        drawerLayout.closeDrawer(GravityCompat.START);
        return true;
    }