ArgumentOutOfRangeException error is thrown in the console.

Steps to repro:
1. Create a new HDRP template project.
2. Windows > Render Pipeline > Look Dev.
3. Create a New Environment Library.
4. Add a new Empty Environment.
5. Click on the Duplicate Environment tab.

Actual Result:
-Unable to duplicate currently selected Environment Library.
-ArgumentOutOfRangeException error is thrown in the console.

Expected Result:
New Environment library should be created without any errors.

Reproducible in:
2021.2.0a6, 2021.2.0a5 with Package version 12.0.0.

Working Fine in:
2021.2.0a4 with Package version 12.0.0.
2021.1.0b8 with package version 11.0.0.

Environment:
Occurring on Windows 10 & Mac 10.15.

Stack trace:
ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index