[FIX] sale_timesheet: set wrong code on analytic line

The product_id is the one of the timesheet line, not the one of the order (which
actually is the one of the first line).
Closes #12013

addons/sale_timesheet/models/sale_timesheet.py

@@ -127,7 +127,7 @@ class SaleOrder(models.Model):
             if not order.project_id:
                 for line in order.order_line:
                     if line.product_id.track_service == 'timesheet':
-                        order._create_analytic_account(prefix=order.product_id.default_code or None)
+                        order._create_analytic_account(prefix=line.product_id.default_code or None)
                         break
         return result