When the `purchase.order` is added as an embedded tree view on a model without a `state` field, a crash occurs. The existing condition doesn't make sense on a PO (while it would make sense on a PO line), so we simply remove it. Since the condition implied that the field `invoice_status` was always hidden, we keep it that way. opw-2005768 closes odoo/odoo#33827 Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>