[FIX] stock_account: zero quantity

- Set up a stockable product for which the product category is FIFO / Perpetual
- Create a PO for this product with a unit price of 100$
- Confirm the purchase order
- Receive the item in stock
- Create a SO for this product
- Confirm the SO
- Deliver the item
- Unlock the delivery order and change the done quantity to 0
- Unlock the delivery order and change again the done quantity to a positive value

A `ZeroDivisionError` is raised.

Since `move.product_qty` is still zero, we fallback to `quantity`.

opw-1963984

closes odoo/odoo#32421

Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>

addons/stock_account/models/stock.py

@@ -303,7 +303,7 @@ class StockMove(models.Model):
         if qty_to_take_on_candidates == 0:
             move.write({
                 'value': -tmp_value if not quantity else move.value or -tmp_value,  # outgoing move are valued negatively
-                'price_unit': -tmp_value / move.product_qty,
+                'price_unit': -tmp_value / (move.product_qty or quantity),
             })
         elif qty_to_take_on_candidates > 0:
             last_fifo_price = new_standard_price or move.product_id.standard_price