Unselecting all the Blog categories for a Blog Post doesn't work

Steps to reproduce:

1. Create a new blog post and select all 3 categories (News, Other & Personal)
2. Save & View
3. Edit and unselect all 3 categories
4. Save & View
5. Edit and check the Category section -> all 3 categories are still selected
6. Unselect 1 or 2 categories
7. Save & View
8. Edit and check the Category section -> the modifications from step 6 are visible