[FIX] sale: fix get_combination_info RPC when product_id given

Follow up of 51ef8514ea

The RPC would fail to return the correct value for `is_combination_possible` if
a product_id is given instead of a combination.

opw-2003069

closes odoo/odoo#33677

Signed-off-by: Sébastien Theys <seb-odoo@users.noreply.github.com>

addons/sale/controllers/product_configurator.py

@@ -48,6 +48,10 @@ class ProductConfiguratorController(http.Controller):
         res = product_template._get_combination_info(combination, int(product_id or 0), int(add_qty or 1), pricelist)
         if 'parent_combination' in kw:
             parent_combination = request.env['product.template.attribute.value'].browse(kw.get('parent_combination'))
+            if not combination.exists() and product_id:
+                product = request.env['product.product'].browse(int(product_id))
+                if product.exists():
+                    combination = product.product_template_attribute_value_ids
             res.update({
                 'is_combination_possible': product_template._is_combination_possible(combination=combination, parent_combination=parent_combination),
             })