Reproduction steps:
1. Create new project.
2. Create empty GameObject.
3. Add Cloth component to GameObject.
4. Create any 3D object (Plane)
5. Add Cloth component to 3D object.

Expected result: Component will be added.
Actual result: Unity crashes.

Note: If you change 4-5 steps with 2-3, after creating new 3D object, Unity will crash.

Reproduced on: 5.6.0a6, 5.6.0b3, 5.6.0b6.
Works fine on: 5.5.0f3, 5.5.1p3.
Regression introduced in 5.6.