Estou tendo um erro quando quero abrir uma página simples. Este é o erro completo:

ContextErrorException: Erro fatal detectável: o objeto da classe __PHP_Incomplete_Class não pôde ser convertido em string em /Applications/mampstack-5.4.20-0/apache2/htdocs/engelsvandenbroecke/vendor/symfony/symfony/src/Symfony/Component Autenticação / Token / AbstractToken.php linha 70

O que eu fiz no meu projeto symfony é:

Gerar entidades do banco de dadosEditar entidade do usuário para segurançaEdite security.ymlAdicionado dois fixadores de dados

Esta é minha classe de entidade do usuário:

<?php

namespace Beachteam\BeachteamBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Symfony\Component\Security\Core\User\AdvancedUserInterface;

/**
 * User
 *
 * @ORM\Table(name="user", uniqueConstraints={@ORM\UniqueConstraint(name="username_UNIQUE", columns={"username"})}, indexes={@ORM\Index(name="fk_users_roles_idx", columns={"role_id"})})
 * @ORM\Entity
 */
class User implements AdvancedUserInterface
{
    /**
     * @var string
     *
     * @ORM\Column(name="username", type="string", length=45, nullable=false)
     */
    private $username;

    /**
     * @var string
     *
     * @ORM\Column(name="password", type="string", length=60, nullable=false)
     */
    private $password;

    /**
     * @var string
     *
     * @ORM\Column(name="salt", type="string", length=30, nullable=false)
     */
    private $salt;

    /**
     * @var string
     *
     * @ORM\Column(name="firstname", type="string", length=45, nullable=false)
     */
    private $firstname;

    /**
     * @var string
     *
     * @ORM\Column(name="surname", type="string", length=45, nullable=false)
     */
    private $surname;

    /**
     * @var string
     *
     * @ORM\Column(name="email", type="string", length=255, nullable=false)
     */
    private $email;

    /**
     * @var string
     *
     * @ORM\Column(name="token", type="string", length=45, nullable=true)
     */
    private $token;

    /**
     * @var \DateTime
     *
     * @ORM\Column(name="created", type="datetime", nullable=false)
     */
    private $created;

    /**
     * @var integer
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="IDENTITY")
     */
    private $id;

    /**
     * @var \Beachteam\BeachteamBundle\Entity\Role
     *
     * @ORM\ManyToOne(targetEntity="Beachteam\BeachteamBundle\Entity\Role")
     * @ORM\JoinColumns({
     *   @ORM\JoinColumn(name="role_id", referencedColumnName="id")
     * })
     */
    private $role;

    private $plainPassword;

    /**
     * Constructor
     */
    public function __construct()
    {
        $this->salt = base_convert(sha1(uniqid(mt_rand(), true)), 16, 36);
    }


    /**
     * Set username
     *
     * @param string $username
     * @return User
     */
    public function setUsername($username)
    {
        $this->username = $username;

        return $this;
    }

    /**
     * Get username
     *
     * @return string 
     */
    public function getUsername()
    {
        return $this->username;
    }

    /**
     * Set password
     *
     * @param string $password
     * @return User
     */
    public function setPassword($password)
    {
        $this->password = $password;

        return $this;
    }

    /**
     * Get password
     *
     * @return string 
     */
    public function getPassword()
    {
        return $this->password;
    }

    /**
     * Set salt
     *
     * @param string $salt
     * @return User
     */
    public function setSalt($salt)
    {
        $this->salt = $salt;

        return $this;
    }

    /**
     * Get salt
     *
     * @return string 
     */
    public function getSalt()
    {
        return $this->salt;
    }

    /**
     * Set firstname
     *
     * @param string $firstname
     * @return User
     */
    public function setFirstname($firstname)
    {
        $this->firstname = $firstname;

        return $this;
    }

    /**
     * Get firstname
     *
     * @return string 
     */
    public function getFirstname()
    {
        return $this->firstname;
    }

    /**
     * Set surname
     *
     * @param string $surname
     * @return User
     */
    public function setSurname($surname)
    {
        $this->surname = $surname;

        return $this;
    }

    /**
     * Get surname
     *
     * @return string 
     */
    public function getSurname()
    {
        return $this->surname;
    }

    /**
     * Set email
     *
     * @param string $email
     * @return User
     */
    public function setEmail($email)
    {
        $this->email = $email;

        return $this;
    }

    /**
     * Get email
     *
     * @return string 
     */
    public function getEmail()
    {
        return $this->email;
    }

    /**
     * Set token
     *
     * @param string $token
     * @return User
     */
    public function setToken($token)
    {
        $this->token = $token;

        return $this;
    }

    /**
     * Get token
     *
     * @return string 
     */
    public function getToken()
    {
        return $this->token;
    }

    /**
     * Set created
     *
     * @param \DateTime $created
     * @return User
     */
    public function setCreated($created)
    {
        $this->created = $created;

        return $this;
    }

    /**
     * Get created
     *
     * @return \DateTime 
     */
    public function getCreated()
    {
        return $this->created;
    }

    /**
     * Get id
     *
     * @return integer 
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * Set role
     *
     * @param \Beachteam\BeachteamBundle\Entity\Role $role
     * @return User
     */
    public function setRoles(\Beachteam\BeachteamBundle\Entity\Role $role = null)
    {
        $this->role = $role;

        return $this;
    }

    /**
     * Get role
     *
     * @return \Beachteam\BeachteamBundle\Entity\Role 
     */
    public function getRoles()
    {
        return array($this->role->getName());
    }

    public function eraseCredentials()
    {
        $this->setPlainPassword(null);
    }

    public function getPlainPassword()
    {
        return $this->plainPassword;
    }

    public function setPlainPassword($plainPassword)
    {
        $this->plainPassword = $plainPassword;
    }

    /**
     * Implementation of AdvancedUserInterface method
     *
     * @return boolean
     */
    public function isAccountNonExpired()
    {
        return true;
    }

    /**
     * Implementation of AdvancedUserInterface method
     *
     * @return boolean
     */
    public function isAccountNonLocked()
    {
        return true;
    }

    /**
     * Implementation of AdvancedUserInterface method
     *
     * @return boolean
     */
    public function isCredentialsNonExpired()
    {
        return true;
    }

    /**
     * Implementation of AdvancedUserInterface method
     *
     * @return boolean
     */
    public function isEnabled()
    {
        return true;
    }
}

Meu security.yml:

    security:
encoders:
    Beachteam\BeachteamBundle\Entity\User:
        algorithm: bcrypt
        cost: 15

role_hierarchy:
    ROLE_SUPER_ADMIN: ROLE_ADMIN

providers:
    users:
        entity:
            class: BeachteamBundle:User
            property: username

firewalls:
    dev:
        pattern:  ^/(_(profiler|wdt)|css|images|js)/
        security: false

    secured_area:
        pattern: ^/
        anonymous: ~
        form_login:
            login_path: beach_team_loginpage
            check_path: beach_team_logincheck
            username_parameter: login[username]
            password_parameter: login[password]
            always_use_default_target_path: true
            default_target_path: beach_team_adminpage
        logout:
            path:   beach_team_logout
            target: beach_team_loginpage
        remember_me:
             key:      "%secret%"
             lifetime: 31536000 # 365 days in seconds
             path:     /
             domain:   ~ # Defaults to the current domain from $_SERVER
             remember_me_parameter: remember

access_control:
    #- { path: ^/login, roles: IS_AUTHENTICATED_ANONYMOUSLY, requires_channel: https }