[FIX] product: prevent traceback on removing quantity of product in quotation

When user removes the quantity of product and tries to confirm the product
in configure wizard,
a traceback will appear.

Steps to reproduce the error:
- Go to Sales > Configuration > Settings
  > Product Catalog > enable Variant Grid Entry
  > Pricing > enable Pricelists (Advanced price rules)
- Go to products > pricelist > open any pricelist > Add a line
  > set value of Min. Quantity
- Create new Quotation > Select that pricelist > Add a product
  > Select a product that has variants (ex. Conference Chair)
  > In configure wizard, remove quantity > Confirm

Error: A traceback appears:
"TypeError: '<' not supported between instances of 'NoneType' and 'float' "

https://github.com/odoo/odoo/blob/fe79e1b5fdc408d55bbb3ac11209163436c1fa2c/addons/product/models/product_pricelist_item.py#L319
Here, when user removes quantity of product,
qty_in_product_uom will be None.
So it will lead to above traceback.

sentry-4547178082

closes odoo/odoo#141523

X-original-commit: 09ff54f1d90be5ef5f2e76deaa481f263c6c75c9
Signed-off-by: Victor Feyens (vfe) <vfe@odoo.com>

addons/sale_product_configurator/controllers/main.py

@@ -139,7 +139,7 @@ class ProductConfiguratorController(Controller):
             product or product_template,
             pricelist,
             combination,
-            quantity=quantity,
+            quantity=quantity or 0.0,
             uom=product_uom,
             currency=currency,
             date=datetime.fromisoformat(so_date),