Issue

The book on the enchanting table will look towards the player, even if it is completely invisible and is wearing no armor pieces (or holding anything in their hands).

Even though this is a very niche scenario, this mechanic can be used in PvP (as an example), where the player can replace the floor with enchanting tables at places to catch other invisible players.

Fixing this issue will also make a lot of sense realistically, as it doesn't make sense for the book to see invisible players.

See the screenshots attached for a visual example. One image has the Glowing effect applied so that you can see where the player is, but the other does not have it applied. They are named respectively.

Expected Behavior

The book should stay shut and not look at the player if they have the invisibility effect applied (and maybe have no armor applied).

How to Reproduce

1. Place an enchanting table down in a flat area.
2. Walk away from it and run the command: 

   /effect give @s minecraft:invisibility 30 0 false

3. Come within around 2.5 blocks of the enchanting table.
4. Note how even with the invisibility effect, the book opens and looks at the player.