I've added a 'products' custom post type and a category that is used on posts of that type. The blog page categories widget lists the category even though there are no normal blog posts in that category. When you click on the category you get the "Nothing found" post.
Is there a simple way to prevent such categories from appearing in the widget? I know can filter them out using query_posts, but I need to know the category ids for that. I just want categories with no normal posts to not display.