Hi, I have to migrate a custom module from V8 to V9 but I have a problem with a medod:

When i'm on a quotation (sales) and i wanna add an item on the sale order line, I've this error :

File "/usr/local/lib/python2.7/dist-packages/odoo-9.0c-py2.7.egg/openerp/addons/WIPv9/sale.py", line 110, in product_id_change if self.product: AttributeError: 'sale.order.line' object has no attribute 'product'

This is the begining of the code (sale.py) where the error comes from :

class sale_order_line(models.Model):
    _inherit = 'sale.order.line'

    @api.multi
    @api.onchange('product_id')
    def product_id_change(self):
        result = super(sale_order_line, self).product_id_change()
        if self.product:

The problem is the 7th line and i have to write it otherwise . Thanks in advance.