Add missing use of ReflectionClass

Author: AngelFQC

src/Chamilo/UserBundle/Entity/User.php

@@ -14,6 +14,7 @@
 use Doctrine\ORM\Mapping as ORM;
 use FOS\UserBundle\Model\GroupInterface;
 use FOS\UserBundle\Model\UserInterface;
+use ReflectionClass;
 use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
 use Symfony\Component\HttpFoundation\File\File;
 use Symfony\Component\Validator\Constraints as Assert;