Repro Steps:
1- Open the attached example using Unity version 2020.2.6f1
2- Click on the asset named "10-TutorialPage".
3- Go to the Completion Criteria section. Add a new criterion. Try to pick the type.

Result:
Null reference will show up. Doing the same in 2020.2.5 causes no error.

Expected:
No errors should be thrown

Repro: 2020.2.6f1
Not Repro: 2020.2.0f1, 2020.2.4f1 , 2020.2.5f1 , 2021.1.0a7