Hi,

When I validate an invoice, the following error appears: AssertionError: convert amount from unknown Currency.

I noticed that in the sale_order_line table, which is linked to the invoice, the currency_id was null instead of having a value. I manually set the correct value, and the invoice was then successfully validated.

I would like to prevent this issue from happening again, specifically avoiding a null value in the currency_id. What can I do to fix this, and what might be the reason why currency_id was null in the first place?