When the "Look Dev" window is opened and "Scriptable Render Pipeline" Asset is set to "None" from the Graphics Settings, then it causes the editor to throw NullReferenceException continuously, refer attached video and LookDev_NullReferenceException_StackTrace.docx

Steps to repro:
1. Create a new project with HDRP Template
2. Window > Render Pipeline > Look Dev
3. Edit > Project Settings > Graphics
4. Scriptable Render Pipeline Settings > None

Actual Result:
NullReferenceException is thrown continuously when Look Dev window is opened and SRP Asset set to None

Expected Result:
"Scriptable Render Pipeline" Asset is set to "None" without any errors when the "Look Dev" window is opened

Reproducible in:
2020.2.0a11, 2020.1.0b8, 2019.3.13f1 with Package Version 9.0.0, 8.1.0, 8.0.1, 7.3.1

Environment:
Occurring on Windows 10 & macOS 10.15