ArgumentException: Invalid path error is thrown on opening UIElements Editor window when any object is selected in Hierarchy. refer to the attached video.

Steps to repro:
1. Create a new Project.
2. Hierarchy > Select Main Camera or Directional Light
2. Assets > Create > UIElements > Editor window.

Actual Result:
ArgumentException error in the console.

Expected Result:
No error in the console.

Reproducible in:
2020.2.0a2, 2020.1.0b1, 2019.3.5f1, 2019.1.0a10

Note: The "UIElements Editor window" Button accessible from 2019.1.0a10 onwards

Environment:
Windows 10 and macOS 10.14