Por que o prestashop não salva minha modificação no banco de dados? Usando prestashop 1.7

/override/classes/Product.php

class Product extends ProductCore {
public $por_gan; public function __construct ($idProduct = null, $idLang = null, $idShop = null) {
$definition = self::$definition;
$definition['fields']['por_gan'] = array('type' => self::TYPE_INT, 'required' => false);

parent::__construct($idProduct, $idLang, $idShop); } }

Em ProductInformation.php

->add('por_gan', 'Symfony\Component\Form\Extension\Core\Type\NumberType', array(
        'required' => false,
        'label' => $this->translator->trans('Beneficio', [], 'Admin.Catalog.Feature'),
        'constraints' => array(
            new Assert\NotBlank(),
            new Assert\Type(array('type' => 'numeric'))
        ),          
    ))

Em form.html.twing

<div class="col-md-6">
        <label class="form-control-label">% de beneficio</label
        {{ form_widget(form.step1.por_gan) }}
</div>

obrigado