Monsters and other underground mobs can naturally spawn in Trial Chambers

Monsters and other underground mobs such as bats and glow squids can spawn inside the trial chambers. Trial chambers are supposed to be isolated from those naturally spawned monsters to prevent creepers and other unintended mobs to fill the trial chambers.

Steps to Reproduce:

1. Locate a trial chamber and teleport to the x and z coordinates.
2. Switch and go down in spectator mode until you see the trial chamber.
3. Give yourself night vision status effect.
4. Switch to creative mode after going to one of the rooms.

Expected Result
Monsters and other underground mobs (bats & glow squids) should not naturally spawns in trial chambers.

Observed Result
Monsters and other underground mobs (bats & glow squids) naturally spawns inside the trial chambers.