How to reproduce:
1. Open the "Breakable_Crash.zip" project
2. Open the "SimpleCity.unity" scene
3. Enter Play Mode
4. In Scene view Drag ColaMachine game object through Window game object
5. Exit Play Mode
6. Enter Play Mode
7. Repeat step 4

Actual result: Unity crashes. (gif attached)

Reproducible with: 2018.3.0a4, 2018.2.0f2, 2018.1.8f1, 2017.4.7f1, 2017.3.0b10
Regression introduced in: 2017.3.0b10.
Not reproducible with: 2017.3.0b9, 2017.2.3p2.

Note:
After exiting Play Mode first-time error appears: Assertion failed: Assertion failed on expression: 'm_Shape == NULL'
The error and the crash are caused by line: mf.mesh = m; BreakableWindow.cs: 150

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Fixed in 2018.3.0a6, 2018.2.4f1.