On selecting "Update UIElements Schema" from Assets menu cause the editor to throw ArgumentException, refer the attached video

Steps to repro:
1. Create a new project and import 2D PSD Importer
2. Assets > Update UIElements Schema

Actual Result:
ArgumentException thrown when Update UIElements Schema is selected from Assets menu

Expected Result:
UIElements Schema updated gracefully

Occurring on:
2019.3, 2020.1, 2020.2 (3.xx and 2.xx PSD Importer versions)

Environment:
Windows 10 & macOS 10.14