The comparator signal for Chiseled bookshelf is buggy.

After placing all 6 books in the chiseled bookshelf and removing them all, while placing a comparator, it still gives a redstone signal of 1. This can be fixed by replacing the chiseled bookshelf on that area.

Steps to reproduce:

1) Place a Chiseled Bookshelf.
2) Place a comparator next to the Chiseled Bookshelf.
3) Place all 6 books.
4) Remove all 6 books.

Observed results:

After removing all 6 books fron the Chiseled Bookshelf, the comparator still produces a signal of 1. This can be fixed by breaking and again placing the chiseled bookshelf on that area. Then again the bug occurs after placing books.

Expected results:

After removing all 6 books from the chiseled bookshelf, the comparator must produce a signal of 0.