When the "Look Dev" window is opened and the High Definition RP package is upgraded from 7.1.8 to 7.2.0/7.2.1 , causes the editor to throw multiple exceptions continuously and "Look Dev" window turns to white, refer the attached video.

Steps to repro:
1. Create a new project with HDRP Template
2. Window > Render Pipeline > Look Dev
3. Select the "Environment" tab > New Library > Load Library
4. Add new empty environment (+)
5. Keep "Look Dev" window opened
6. Upgrade HDRP package from 7.1.8 to 7.2.1

Actual Result:
Multiple exceptions are thrown continuously on upgrading HDRP package from 7.1.8 to 7.2.1

Expected Result:
Upgrading package doesn't affect anything to "Look Dev" window

Note: "Look Dev" window is introduced in Unity 2019.3.0a12

Reproducible in:
2020.1.0a24, 2019.3.2f1, 2019.3.0a12

Package version found: 7.2.1, 7.1.8, 7.1.7, 7.1.6, 7.1.1, 7.0.0

Note: When packages upgraded from 7.0.0 to 7.1.5, 7.1.6 to 7.1.8, MissingRefernceException is being thrown

Environment:
Windows 10 and macOS 10.14