Resetting the Shadow Caster 2D" component causes the editor to throw UnassignedReferenceException, refer to the attached video.

Steps to repro:
1. Create a new project
2. Hierarchy > Create Empty GameObject
4. Add "Shadow Caster 2D" component in the Inspector
5. Inspector > Shadow Caster 2D > EditShape > Click
6. Scene > Edit edges
7. Inspector > Shadow Caster 2D > Reset

Actual Result:
UnassignedReferenceException is thrown on resetting the "Shadow Caster 2D" component.

Expected Result:
The "Shadow Caster 2D" component is reset without any errors.

Tested with Unity versions:
2020.2.0a2, 2020.1.0b1 , 2019.3.1f2, 2019.3.0b4

Package found version: 8.0.1, 7.2.0 7.1.8, 7.1.5, 7.1.1

Note: The "Shadow Caster 2D" component is introduced in 7.1.1 package

Environment:
Windows 10 & macOS 10.14