Try to delete this entity and regenerate them with next command:
php app/console doctrine:generate:entity --entity="EvrHomeBundle:Article" --fields="name:string(255) content:text exclusive_content:text creation_date:date views:integer votes:integer"
And then add manually:
/**
*
* @ORM\ManyToOne(targetEntity="Subategory",inversedBy="articles")
* @ORM\JoinColumn(name="subcategory_id",referencedColumnName="id")
*/
private $subcategory;