The crash appears only if both parent and child GameObjects have a Wheel Collider component and the parent GameObject has a Rigidbody component which is positioned before Wheel Collider component in the Inspector window.

Reproduction steps:
1. Open Unity editor and create a new project
2. In the Hierarchy window create an empty GameObject (will be called parent GameObject for clarity)
3. Add Rigidbody component to the parent GameObject
4. Add Wheel Collider component to the parent GameObject
5. In the Hierarchy create an empty GameObject as a child to the parent GameObject
6. Add Wheel Collider component to the child GameObject
7. Save the scene
8. In the Inspector window disable parent GameObject

Actual result: Editor crashes
Expected result: Parent GameObject is disabled

Reproducible with: 5.5.5p2, 5.6.4p4, 2017.1.2p4, 2017.2.1f1, 2017.3.0f2, 2018.1.0a7

Notes:
As a workaround in the Inspector window move parent Gameobject's Wheel Collider above its Rigidbody component

Fixed in: 2018.2.0a8