Comment 3 for bug 1897356

It works for me. Steps to test:
- create a category called "Favorite Authors"
- add two authors
- verify that @Favorite authors:true and :false return the right books.
- add a subcategory and add an author to that subcategory
- verify that @Favorite authors:true does not find books by the author in the subcategory
- verify that @Favorite authors:.true does find books by all the authors