Nether stars can be destroyed by anvils

Closely relates to MC-212764 and MC-248613.

The bug

Despite being impervious to explosions, nether stars can still be deleted by a falling anvil.

How to reproduce

1. Throw a nether star on the ground
2. Place an anvil far above it such that it falls onto the nether star
3. Cry as one of the most valuable items in the game is gone forever due to the work of your own hands

Expected results

The nether star would not be destroyed by the anvil.

Actual results

It gets destroyed anyway.