Problem Username could not be found

[jdessaint]

Thank you for your useful Bundle. I followed your documentation about the installation of the CAS client and i think that i misunderstood something.
When I return to my application (after login), I have a message like this :

{"message":"Username could not be found."}

I just created a new Symfony 3.4 project and I did the configuration like in your documentation. So in your CasAuthenticator, I add a var_dump :

`public function getUser($credentials, UserProviderInterface $userProvider){

    if (isset($credentials[$this->username_attribute])) {
        var_dump($userProvider);
        return $userProvider->loadUserByUsername($credentials[$this->username_attribute]);
    } else {
        return null;
    }
}`

And surprise, it returns :

object(Symfony\Component\Security\Core\User\InMemoryUserProvider)#241 (1) {
["users":"Symfony\Component\Security\Core\User\InMemoryUserProvider":private]=>
NULL
}
{"message":"Username could not be found."}

I don't understand why the provider is NULL. For the precision, it's the default userProvider use in your Bundle.
Thank you for your answer.