[FIX] account: display correct price_unit with 100% taxes

Currently, when modifying an invoice line and setting taxes
(price included) for 100%, the price_unit field will
be displayed as 0.

This is incorrect and is being fixed here.

opw-2793284

closes odoo/odoo#88180

X-original-commit: 674eaa3bc10210d34a02145529516da1fa1c1b66
Signed-off-by: Laurent Smet <las@odoo.com>

addons/account/models/account_move.py

@@ -3894,8 +3894,9 @@ class AccountMoveLine(models.Model):
                 'discount': 0.0,
                 'price_unit': amount_currency / (quantity or 1.0),
             }
-        elif not discount_factor:
-            # balance of line is 0, but discount  == 100% so we display the normal unit_price
+        elif not discount_factor or not amount_currency:
+            # balance of line is 0, but discount == 100% or taxes (price included) == 100%,
+            # so we display the normal unit_price
             vals = {}
         else:
             # balance is 0, so unit price is 0 as well