When Skinning Editor is selected in the Sprite Editor window and 2DAnimation package is updated, it cause the Sprite Editor window to turn blank along with Exception ,refer attached video and .PSB file

Steps to Reproduce:
1. Create a New Project with 2D Template
2. Import .PSB file in the project.
3. Window > 2D > Sprite editor.
4. project > Fei_Cel_group.PSB .
5. Sprite editor > Skinning Editor
6. Package manager > 2DAnimation Package Update 4.2.2

Actual Result:
Sprite Editor window turns blank along with "Assertion failed" exception

Expected Result:
No errors in console and Sprite Editor window works gracefully

Workaround: Reopen Sprite Editor window

Note: Updating 4.1.1 to 4.2.1 it working fine

Reproducible on:
2020.2.0a8, 2020.2.0a5, 2020.1.0b8, 2020.1.0b5

Working fine on:
2020.2.0a4, 2020.1.0b4

Package Found version: 4.2.2

Package working fine version: 4.2.1

Environment:
Windows 10 and macOS 10.15