Blog categories counter doesn't properly work when adding a post to a subcategory

Steps to reproduce:

1. Edit the Blog Categories (http://localhost:8080/xwiki/bin/view/Blog/ManageCategories) and add 4 new subcategories to one of the Main categories -> blogCat.png
2. Edit the First blog post (http://localhost:8080/xwiki/bin/edit/Blog/BlogIntroduction) and select subcategory 4
3. Save & View

You'll notice in the "Blog Categories" panel on the left that there's a (1) for subcategories 4 and 3 -> blogCat2.png. I don't think this behaviour is correct. We should have one of these 2 use cases:

• select 4 and only 4 remains selected
• select 4 and all of the parent subcategories (3, 2, 1 & Personal) are also selected