In Cubemap NullReferenceException is thrown on Right Mouse clicking in six textures (Right, Top, Front, Left, Bottom, Back) refer to the attached video

Steps to Repro:
1. Create a new Project
2. Project > Create > Legacy > Cubemap
3. Select New Cubemap > Inspector > six textures (Right, Top, Front, Left, Bottom, Back) > Mouse Right-click

Actual Result:
Error is thrown in the console

Expected Result:
No error in the console.

Reproducible in:
2020.2.0a16

Working Fine in:
2020.2.0a15, 2021.1.6f1

Environment:
Ubuntu 18.04 LTS ,Windows 10 & Mac 10.15.