upload/catalog/controler/common/seo_url.php

Currently there is a problem causing Duplicate content in search engines

When SEO URLs is enabled

example

www.domain.com/existing-category/non-existent-product

Instead of displaying a 404 error page because the product does not exist, it displays the category.

If the non-existent-product used to exist and has been indexed by search engines, now when it is crawled, the category page is picked up as duplicate content.