[FIX] product: Only trigger unlink when there are records to unlink

closes odoo/odoo#92663

X-original-commit: 9039380f74984878f95a4dcf9cf425a855330a38
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/product/models/product_attribute.py

@@ -382,7 +382,8 @@ class ProductTemplateAttributeLine(models.Model):
             # re-use a value that was archived at a previous step.
             ptav_to_activate.write({'ptav_active': True})
             ptav_to_unlink.write({'ptav_active': False})
-        ptav_to_unlink.unlink()
+        if ptav_to_unlink:
+            ptav_to_unlink.unlink()
         ProductTemplateAttributeValue.create(ptav_to_create)
         self.product_tmpl_id._create_variant_ids()