When an expense sheet move is created, there is only one outstanding line, but it is usual to pay separately. That makes the reconciliation step harder. This makes sure one outstanding line is created per invoice_line and then if only one payment is made it can go through the same process as a batch payment Task-3292188 closes odoo/odoo#120450 Related: odoo/upgrade#4625 Signed-off-by: Laurent Smet <las@odoo.com>