Dear all, I ask another help on Odoo v14.

In the purchase order I don't want to use the name of the product, but the internal reference. So I supposed that going in "Reports > Purchase Order > Views > report_purchaseorder_document" I had to change this value:

with this:

This edit doesn't work, an error occured. Reading on this forum, I found a lot of people that wrote to use "l." (instead of "line."), but these tips were for old versions of Odoo. Also trying with "l." the pdf printing has the same error.

The error is above. Could anyone kindly help me to understand why it doesn't like default_code? Thank you very much!

Error to render compiling AST
AttributeError: 'NoneType' object has no attribute '_fields'
Template: purchase.report_purchaseorder_document
Path: /t/t/div/table/tbody/t[2]/tr/t[1]/td[1]/span
Node: