Shulker boxes drop their contents when broken

The bug:

Shulker boxes drop their content on break

Steps to reproduce:

1. Obtain a shulker box
2. Place the shulker box
3. Open it and fill it with random content
4. Break the shulker box in survival with proper tool

Observed behavior:

The shulker box drops all its content and the shulker box item remains empty

Expected behavior:

The shulker box should keep it's content when broke