ArgumentException: Invalid path error is thrown on opening UIElements Editor window.

Steps to repro:
1. Create a new Project.
2. Assets > Create> UIElements > Editor window.

Actual Result:
ArgumentException error in the console.

Expected Result:
No error in the console.

Reproducible in:
2020.1.0a18, 2020.1.0a11.

Working Fine in:
2020.1.0a10, 2019.3.0f5

Environment:
Occurs on Windows and Mac.

Stack trace:
ArgumentException: Invalid path
System.IO.Path.GetDirectoryName (System.String path) (at <437ba245d8404784b9fbab9b439ac908>:0)
UnityEditor.UIElements.UIElementsEditorWindowCreator.init () (at <abcb5714b99e4fb3a117425953eb603c>:0)
UnityEditor.UIElements.UIElementsEditorWindowCreator.CreateTemplateEditorWindow () (at <abcb5714b99e4fb3a117425953eb603c>:0)