[7.0][addons]Order lines to invoice can relaunch a sale.order workflow already done

Hello,

rev addons : 9351

Settings:
- install sale, account and stock addons
- active Settings / Configuration / Sales / Invoicing Process / Generate invoices based on the sales order lines

Steps :
- create a sale order with 'create invoice' on 'on delivery order'
- confirm the sale
- validate the delivery order to 'delivered'
--> the sale.order is now 'done'.

- go to : 'Sales / Invoicing / Order lines to invoice'
- select an order line from your sale.order, make an invoice.
--> this action acts on 'sale.order' state, the sale.order is now in state 'progress'.

I find it misleading, the state 'done' on sale.order workflow is a 'flow_stop' step.

Romain