[FIX] sale: onchange on 'note' in a sale order

When website_quote is installed, the Terms and Conditions of the quote
template should replace the Terms and Conditions of the company.
But if T&C of the company is not filled, it will keep the note written.

opw:683543

addons/sale/sale.py

@@ -207,8 +207,9 @@ class SaleOrder(models.Model):
             'payment_term_id': self.partner_id.property_payment_term_id and self.partner_id.property_payment_term_id.id or False,
             'partner_invoice_id': addr['invoice'],
             'partner_shipping_id': addr['delivery'],
-            'note': self.with_context(lang=self.partner_id.lang).env.user.company_id.sale_note,
         }
+        if self.env.user.company_id.sale_note:
+            values['note'] = self.with_context(lang=self.partner_id.lang).env.user.company_id.sale_note
 
         if self.partner_id.user_id:
             values['user_id'] = self.partner_id.user_id.id