[FIX] product: exclude without attribute values

With the demo data:
- Go to Sale > Products > Products, search for 'Customizable Desk'
- Click on 'Configure Variants'
- For variant 'Legs: Steel', remove the attribute values for the
  'Conference Chair'
- Create a SO, add a line with 'Configure Product'
- Select the 'Customizable Desk' with 'Legs: Steel', add

The 'Conference Chair' is displayed in the 'Available Options', while it
shouldn't.

The methods `_get_own_attribute_exclusions` and
`_get_parent_attribute_exclusions` compute the exclusions based on the
attribute values. Since there is no values in our case, the exclusion is
not taken into account.

We add a specific case to search for exclusions without values.

opw-1945460

addons/product/models/product_template.py

@@ -730,6 +730,19 @@ class ProductTemplate(models.Model):
         self.ensure_one()
         if not parent_combination:
             return []
+
+        # Search for exclusions without attribute value. This means that the template is not
+        # compatible with the parent combination. If such an exclusion is found, it means that all
+        # attribute values are excluded.
+        if parent_combination:
+            exclusions = self.env['product.template.attribute.exclusion'].search([
+                ('product_tmpl_id', '=', self.id),
+                ('value_ids', '=', False),
+                ('product_template_attribute_value_id', 'in', parent_combination.ids),
+            ], limit=1)
+            if exclusions:
+                return self.mapped('attribute_line_ids.product_template_value_ids').ids
+
         return [
             value_id
             for filter_line in parent_combination.mapped('exclude_for').filtered(