The book GUI isn't closed when switching into spectator mode

The Bug:

The book GUI isn't closed when switching into spectator mode.

Steps to Reproduce:

1. Build the setup shown in the attachment below. setup.png
2. Obtain a book and quill and open your world to LAN.
3. Click on the button to activate the command block and quickly open your book.
4. Take note as to whether or not the book GUI is closed when switching into spectator mode.

Observed Behavior:

The book GUI isn't closed.

Expected Behavior:

The book GUI would be closed.