Text Mesh Pro package "Version 3.0.0-preview.12 - May 11, 2020"

Steps:
1. Import Text Mesh Pro essentials
2. Load "02 - Multi-line TextMesh Pro" scene
3. Convert "Multi Line TextMesh Pro" GameObject to prefab
4. Make an override in "TextMeshPro-Text" component on the instance
5. Switch to InContext mode
6. Remove "TextMeshPro-Text" component
7. Undo
==>
MissingReferenceException: The object of type 'TextMeshPro' has been destroyed but you are still trying to access it.
Your script should either check if it is null or you should not destroy the object.

Not repro in Version 2018.4.23f1 (8a071d16a0e7) + TMP version 1.4.1 (verified)