How to reproduce:
1. Open the project from the attached file "1214031.zip"
2. In the Hierarchy window, select the "Quad" GameObject
3. In the Animation window play the "Anim" animation clip
4. Enter Play Mode and inspect the Console

Expected result: No error in the console is being thrown
Actual result: "MissingReferenceException: The object of type 'AnimationClip' has been destroyed but you are still trying to access it." is thrown in the console

Reproducible with: 2019.3.0a2, 2019.3.0f6, 2020.1.0a19
Could not test with: 2017.4.37f1, 2018.4.17f1, 2019.3.0a1("Enter Play Mode Settings" not introduced)

Note: Reproducible only when going to Edit > Project Settings and enabling Enter Play Mode Options, checking Reload Scene and unchecking Reload Domain