[FIX] stock_account: negative quant cost

- Set up a product with 'Real Price' costing method, in real time
  valuation
- Receive 1000 units at $0.10 each
- Create a landed cost of $456.70, validate => it creates a quants of
  999 units at cost $0.56 and 1 unit at cost $-2.74.
- Perform an inventory adjustment, and set the quantity to 0 instead of
  1000, post inventory.

An error arises due to the constrain debit + credit >= 0.

This is caused by the method `_prepare_account_move_line` from
`stock.move`, which cannot handle negative cost for quants.

opw-752063
Fixes #17707

addons/stock_account/models/stock.py

@@ -312,8 +312,8 @@ class StockMove(models.Model):
             'product_uom_id': self.product_id.uom_id.id,
             'ref': self.picking_id.name,
             'partner_id': partner_id,
-            'debit': debit_value,
-            'credit': 0,
+            'debit': debit_value if debit_value > 0 else 0,
+            'credit': -debit_value if debit_value < 0 else 0,
             'account_id': debit_account_id,
         }
         credit_line_vals = {
@@ -323,8 +323,8 @@ class StockMove(models.Model):
             'product_uom_id': self.product_id.uom_id.id,
             'ref': self.picking_id.name,
             'partner_id': partner_id,
-            'credit': credit_value,
-            'debit': 0,
+            'credit': credit_value if credit_value > 0 else 0,
+            'debit': -credit_value if credit_value < 0 else 0,
             'account_id': credit_account_id,
         }
         res = [(0, 0, debit_line_vals), (0, 0, credit_line_vals)]