Editor Coroutine throws Null Reference Exception when stopping Coroutine

Unity: Cloth

6.0.X

2023.3.X

2023.2.X

2023.1.X

2021.3.X

2020.3.X

After review we have elected not to address this issue at this time.

Reproduction steps:
1. Open user attached Project "EditorCoroutinesBug"
2. Click Tools > "Bug"
3. Click Unsubscribe

Expected result: The Coroutine is stopped
Actual result: A NullReferenceException is thrown

Reproducible with: 2019.4.16f1, 2020.1.17f1, 2020.2.0f1, 2021.1.0a9
Could not test with: 2018.4 (Compiler errors)