[FIX] sale: fix no_variant price extra context propagation

Issue

	- Install Sales
	- Enable discounts & pricelists
	- Create a product
		- 2 variants:
			- first with "create variant" set to Always
			- second set to Never
	- Create a SO
	- Pricelist setting "without_discount"
	- Add the product with product configurator

	The line price is not correct (only Always taken in account)

Cause

	When the variant has Create Variant set to Never
	we pass the extra money in the context.

	When we have a pricelist with "without_discount"
	this context is not propagated correctly and it's lost

Solution

	Pass the product directly if it's not empty which
	have the context set.

OPW-2246102

closes odoo/odoo#52427

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