"Failed to load spawn rules" error when opening Star Wars Mash-Up and Ice Age Mash-Up worlds

Summary:
When opening the Star Wars Mash-Up and Ice Age Mash-Up worlds, the following content log errors appear:

[Entity][error] Star Wars Mash-Up | Failed to load spawn rules
[Entity][error] Ice Age | Failed to load spawn rules

Steps to Reproduce:

1. Enable "Content Log GUI" in Settings > Creator
2. Open the Star Wars Mash-Up or Ice Age Mash-Up world

Observed Results:
A content log error appears.

Expected Results:
No content log error should appear.

Screenshot: