The bottom faces of vaults aren't culled when covered by blocks

The Bug:

The bottom faces of vaults aren't culled when covered by blocks.

Steps to Reproduce:

1. Place down a vault on the ground.
2. Switch to spectator mode and observe the bottom face of the vault.

Observed Behavior:

The bottom faces of vaults aren't culled when covered by blocks.

Expected Behavior:

The bottom faces of vaults would be culled when covered by blocks.