Steps to reproduce:
1. Create a project
2. Add a Sprite in the Hierarchy
3. Add a BoxCollider2D to the Sprite
4. Add a RigidBody2D to the Sprite
5. Add a CompositeCollider2D to the Sprite
6. Play a Scene
7. Stop playing a Scene
8. Remove CompositeCollider2D from the Sprite
9. Observe the error in the Console window:
Assertion failed: Assertion failed on expression: 'm_InstanceID != InstanceID_None'
10. Start clicking on UI elements in the Editor (until Editor will crash)
11. Observe the crash

Expected result: Unity should not crash
Actual result: Unity crashes

Reproduced with: 5.6.0p4, 2017.1.0b3, 2017.1.0b4