Método delete erro HTTP Status 500 - java.lang.IllegalArgumentException: attempt to create delete event with null entity

Criei um projeto de gestão pedagógica e ao usar o método de remoção ele retorna um erro java.lang.IllegalArgumentException: attempt to create delete event with null entity.

Os métodos em si (na minha opnião) não estão com o código errado o erro provavelmente está na jsp.

Postarei aqui os códigos.

Controller

package br.com.tcc.controllers;

import java.util.List;

import javax.inject.Inject;
import javax.validation.Valid;

import br.com.caelum.vraptor.Controller;
import br.com.caelum.vraptor.Post;
import br.com.caelum.vraptor.Result;
import br.com.caelum.vraptor.interceptor.IncludeParameters;
import br.com.caelum.vraptor.validator.Validator;
import br.com.tcc.dao.TurmaDao;
import br.com.tcc.modelos.Turma;

@Controller
public class TurmaController {

    private Result result;
    private Validator validator;
    private TurmaDao turmaDao;

    @Inject
    public TurmaController(Result result, Validator validator, TurmaDao turmaDao) {
        this.result = result;
        this.validator = validator;
        this.turmaDao = turmaDao;
    }

    @Deprecated
    public TurmaController(){    
    }

    public void form(){

    }

    @IncludeParameters
    public void adiciona(@Valid Turma turma){
        validator.onErrorForwardTo(this).form();
        turmaDao.adiciona(turma);
        result.redirectTo(this).lista();
    }

    public void lista(){
        List<Turma> turmas = turmaDao.lista();
        result.include("turmas", turmas);
    }

    @IncludeParameters @Post
    public void remove(Turma turma){
        System.out.println("Id da turma" + turma.getId());
        turmaDao.remove(turma);
        result.redirectTo(this).lista();
    }

    public void formRemocao(){
        result.include("turmas", turmaDao.lista());
    }
}

Dao:

package br.com.tcc.dao;

import java.util.List;

import javax.inject.Inject;
import javax.persistence.EntityManager;
import javax.persistence.TypedQuery;

import br.com.tcc.modelos.Turma;

public class TurmaDao {

    private EntityManager manager;

    @Inject
    public TurmaDao(EntityManager manager) {
        this.manager = manager;
    }

    @Deprecated
    public TurmaDao(){

    }

    public void adiciona(Turma turma){
        manager.getTransaction().begin();

        manager.persist(turma);

        manager.getTransaction().commit();
    }

    public Turma busca(Turma turma) {
        return manager.find(Turma.class, turma.getId());
    }


    public List<Turma> lista(){
        TypedQuery<Turma> query = manager.createQuery("select t from Turma as t",Turma.class);
        return query.getResultList();
    }

public void remove(Turma turma) {
        manager.getTransaction().begin();

        turma = busca(turma);
        manager.remove(turma);

        manager.getTransaction().commit();
    }

    public void altera(Turma turma){
        manager.getTransaction().begin();

        Turma turmaNova = busca(turma);
        turmaNova.setAno(turma.getAno());
        turmaNova.setEtapa(turma.getEtapa());
        turmaNova.setNome(turma.getNome());
        turmaNova.setSerie(turma.getSerie());

        manager.getTransaction().commit();
    }
}

JSPS:

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib tagdir="/WEB-INF/tags" prefix="alura"%>
<c:import url="/WEB-INF/jsp/header.jsp"></c:import>

<form action="${linkTo[TurmaController].remove(null)}" method="post">
    <label for="turmas">Selecione uma turma:</label> 

    <select id="turmas" name="turma">
        <c:forEach var="turma" items="${turmas}">
            <option value="${turma.id}">"${turma.nome}"</option>
        </c:forEach>
    </select> <input type="submit" value="Remover" class="btn" />
</form>

<c:import url="/WEB-INF/jsp/footer.jsp"></c:import>

Na stacktrace reparei que o id não está passando corretamente:

mai 11, 2017 6:20:07 PM org.hibernate.validator.internal.xml.ValidationXmlParser unmarshal
INFO: HV000007: META-INF/validation.xml found. Parsing XML based configuration.
Id da turma 0
Hibernate: 
    select
        turma0_.id as id1_7_0_,
        turma0_.ano as ano2_7_0_,
        turma0_.etapa as etapa3_7_0_,
        turma0_.nome as nome4_7_0_,
        turma0_.serie as serie5_7_0_ 
    from
        Turma turma0_ 
    where
        turma0_.id=?
mai 11, 2017 6:20:07 PM org.apache.catalina.core.StandardWrapperValve invoke
GRAVE: Servlet.service() for servlet [default] in context with path [/pedagogico] threw exception [java.lang.IllegalArgumentException: attempt to create delete event with null entity] with root cause
java.lang.IllegalArgumentException: attempt to create delete event with null entity