How to reproduce:
1. Open the attached project "clothBug"
2. Open the Scene "SampleScene" (Assets/Scenes/SampleScene.unity)
3. In the Hierarchy window, select the "Cylinder" GameObject
4. In the Inspector window, press the "Edit cloth constraints" button under the Cloth Component
5. Enter, then exit Play mode and observe the Console window

Expected result: No errors are shown in the Console
Actual result: NullReferenceException errors are shown in the Console

Reproducible with: 2021.2.0a17, 2021.2.0b15, 2022.1.0a11
Not reproducible with: 2019.4.31f1, 2020.3.19f1, 2021.1.23f1, 2021.2.0a16

Errors in the Console:
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.ClothInspector+SceneViewClothConstraintsOverlay.OnGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/Inspector/ClothInspector.cs:1949)