Na alteração está criando um novo aluno ao invés de alterar os dados

package br.com.alura.agenda;

import android.widget.EditText;
import android.widget.RatingBar;

import br.com.alura.agenda.modelo.Aluno;

/**
 * Created by julio.maggieri on 23/01/2018.
 */

public class FormularioHelper {

    private final EditText campoNome;
    private final EditText campoEndereco;
    private final EditText campoTelefone;
    private final EditText campoSite;
    private final RatingBar campoNota;
    private Aluno aluno;

    public FormularioHelper(FormularioActivity activity){
        campoNome = (EditText) activity.findViewById(R.id.formulario_nome);
        campoEndereco = (EditText) activity.findViewById(R.id.formulario_endereco);
        campoTelefone = (EditText) activity.findViewById(R.id.formulario_telefone);
        campoSite = (EditText) activity.findViewById(R.id.formulario_site);
        campoNota = (RatingBar) activity.findViewById(R.id.formulario_nota);

    }

    public Aluno getAluno() {
        Aluno aluno = new Aluno();
        aluno.setNome(campoNome.getText().toString());
        aluno.setEndereco(campoEndereco.getText().toString());
        aluno.setTelefone(campoTelefone.getText().toString());
        aluno.setSite(campoSite.getText().toString());
        aluno.setNota(Double.valueOf(campoNota.getProgress()));
        return aluno;
    }

    public void preencheFormulario(Aluno aluno) {
        campoNome.setText(aluno.getNome());
        campoEndereco.setText(aluno.getEndereco());
        campoTelefone.setText(aluno.getTelefone());
        campoSite.setText(aluno.getSite());
        campoNota.setProgress(aluno.getNota().intValue());
        this.aluno = aluno;
    }
}



package br.com.alura.agenda;


import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.Toast;

import br.com.alura.agenda.dao.AlunoDAO;
import br.com.alura.agenda.modelo.Aluno;

public class FormularioActivity extends AppCompatActivity {

    private FormularioHelper helper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_formulario);
        helper = new FormularioHelper(this);
        Intent intent = getIntent();
        Aluno aluno = (Aluno) intent.getSerializableExtra("aluno");
        if (aluno != null) {
            helper.preencheFormulario(aluno);
        }


    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu_formulario, menu);
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem  item) {
        switch (item.getItemId()) {
            case R.id.menu_formulario_ok:
                Aluno aluno = helper.getAluno();

                AlunoDAO dao = new AlunoDAO(this);
                if (aluno.getId() != null){
                    dao.altera(aluno);
                } else {
                    dao.insere(aluno);
                }
                    dao.close();


                Toast.makeText(FormularioActivity.this, "Aluno " + aluno.getNome() + " salvo!", Toast.LENGTH_SHORT).show();

                finish();
                break;
        }

        return super.onOptionsItemSelected(item);
    }
}