Prevent ReflectionException when modelClass dont exist in AdminExtension...

When using sonata page bundle a got ReflectionException because Application\Sonata\PageBundle\Entity\Post don't exist, any time i want to generate from easy-extends it throw the ReflectionException and i got a loop of error without solution because i can not create the Application\Sonata\PageBundle\Entity\Post class, with this it avoid the throw of Exception in the origin.