Assets are removed from duplicated world partition levels

Duplicating a world partition level appears to cause all assets within that duplicate to disappear once the duplicate is reloaded

This a not a regression due to being a new feature. 

1. Create a new project with starter content.
2. Enable world partitions in project settings.
3. Create a world partition level.
4. Add assets into the level and save.
5. Duplicated the newly created level and save.
6. Open another level and then reopen the duplicated level.

Result: Assets are removed from the level.

Expected Result: The assets are still present.