When a Range property is created in the SpriteShape profiler preset and Undo/Redo operation is performed then Editor throws NullReferenceException, Refer attached video.

Steps to repro:
1. Create a new project with 2D Template
2. Project window > Create > 2D > SpriteShape profiler
3. Reset SpriteShape profiler asset from the Inspector
4. Create a Preset of SpriteShape profiler
5. Project > SpriteShape preset > Inspector > Create Range
6. Edit > Undo Create Range > Undo Selection Change
7. Edit > Redo Selection Change > Redo Create Range

Actual Result:
NullReferenceException is thrown on performing Redo operation when Range is created in the SpriteShape profiler preset earlier

Expected Result:
Redo operation is performed gracefully

Note: "Create Range" button is available from Package Version 5.0.1.

Reproducible in:
2020.2.0b2, 2020.2.0b1 with Package Version 5.0.1.

Environment:
Occurring on Windows 10 & Mac 10.15.

Stack trace:
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.Editor.get_referenceTargetIndex () (at <3d7c86b365634083bceadac5c7f36490>:0)
UnityEditor.Editor.get_target () (at <3d7c86b365634083bceadac5c7f36490>:0)
UnityEditor.U2D.SpriteShapeEditor.OnEnable () (at library/packagecache/com.unity.2d.spriteshape@5.0.1/editor/spriteshapeeditor.cs:128)