Chiseled bookshelves gives redstone signal based on last interacted slot.

So i was testing these cool features when i suddenly found this bug

 

how to recreate:

1. Place a chiseled bookshelf

2. Place a comparator beside the chiseled bookshelf

3. Put any kind of book in the chiseled bookshelf

4. Lastly remove the book from the chiseled bookshelf

and you should see the results thank you