[android help] Android NullPointerException on onCreateOptionsMenu

This is my code:

public class className extends Activity{
    private MenuActivity menuActivity;

    @Override
    public void onCreate(Bundle savedInstanceState) {

        try {
            ViewConfiguration config = ViewConfiguration.get(this);
            Field menuKeyField = ViewConfiguration.class
                .getDeclaredField("sHasPermanentMenuKey");
            if (menuKeyField != null) {
                menuKeyField.setAccessible(true);
                menuKeyField.setBoolean(config, false);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        menuActivity = new MenuActivity(this, context, R.menu.menu);
        );
    }
    @Override


    public boolean onCreateOptionsMenu(Menu menu) {
        menuActivity.onCreateOptionsMenu(menu);   // <--
        return super.onCreateOptionsMenu(menu);
    }
}

public class MenuActivity {
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = mRootActivity.getMenuInflater();
        inflater.inflate(typeMenu, menu);
        return true;
    }

    public boolean onOptionsItemSelected(MenuItem item) {
    }

    // ...
}

I receive a NullPointerException on row:

menuActivity.onCreateOptionsMenu(menu);

This exception is present only some moble like Galaxy note. Do you know why there is this exception?

.

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