[FIX] account: relax tax scope constraint for tax groups

* Create a tax of type `group` and with a `tax_scope` set
* Add a child tax without `tax_scope` set

This will raise an error because the `tax_scope` is not exactly the same
since it doesn't have a value.
We should be able to share sub taxes without a scope, exactly like for
`type_tax_use`. This is also what the message suggests.

closes odoo/odoo#143089

X-original-commit: 6101b2bbeaf996d4c3472ad36d740243bb0a5aa8
Signed-off-by: Josse Colpaert <jco@odoo.com>
Signed-off-by: William André (wan) <wan@odoo.com>

addons/account/models/account_tax.py

@@ -455,7 +455,11 @@ class AccountTax(models.Model):
         for tax in self:
             if not tax._check_m2m_recursion('children_tax_ids'):
                 raise ValidationError(_("Recursion found for tax %r.", tax.name))
-            if any(child.type_tax_use not in ('none', tax.type_tax_use) or child.tax_scope != tax.tax_scope for child in tax.children_tax_ids):
+            if any(
+                child.type_tax_use not in ('none', tax.type_tax_use)
+                or child.tax_scope not in (tax.tax_scope, False)
+                for child in tax.children_tax_ids
+            ):
                 raise ValidationError(_('The application scope of taxes in a group must be either the same as the group or left empty.'))
 
     @api.constrains('company_id')