Product_cat 404 error in sitemap

Hi

I get an 404 error in google webmasters for : http://www.stickyrc.com/product_cat-sitemap.xml

I have 3 product catgory’s, why does their appear an error and how can I fix this, or is this just a plugin bug?

http://www.stickyrc.com/sitemap_index.xml

Thanks,
Andreas

https://wordpress.org/plugins/wordpress-seo/