[FIX] sale: _get_conversion_rate called with no date

Steps to reproduce the bug:
- Define two pricelists P1(€) the default one and P2($) with discount_policy = 'without_discount'
- Activate P1 and P2 on the website
- Go on the shop and select P2

Bug:

An error was raised from function _get_conversion_rate because the arguments date and company_id were not defined
because the function _get_real_price_currency was called from _website_product_id_change with
the model "self.env['sale.order.line'] and not with a recordset. So the fields self.company_id and self.order_id.date_order
were not defined.

opw:1969849

closes odoo/odoo#32726

Signed-off-by: Simon Goffin (sig) <sig@openerp.com>

addons/sale/models/sale.py

@@ -1578,7 +1578,7 @@ class SaleOrderLine(models.Model):
             if currency_id.id == product_currency.id:
                 cur_factor = 1.0
             else:
-                cur_factor = currency_id._get_conversion_rate(product_currency, currency_id, self.company_id, self.order_id.date_order)
+                cur_factor = currency_id._get_conversion_rate(product_currency, currency_id, self.company_id or self.env.user.company_id, self.order_id.date_order or fields.Date.today())
 
         product_uom = self.env.context.get('uom') or product.uom_id.id
         if uom and uom.id != product_uom: