Editor crashes while stopping Standard_MapsAndMode scene of UTF_Suites_GraphicsGeneral.

Steps to Reproduce:
1. Download the UTF_Suits_GraphicsGeneral project. (https://github.com/Unity-Technologies/UTF_Suites_GraphicsGeneral)
2. Clone Shaders SubModule.
3. Play "Standard_MapsAndMode" scene and stop it.

Observe the Force Quit Pop-up with the following message:
"CheckDisalowAllocation.Allocating memory when it is not allowed to allocate memory."

Reproduced On: 2018.1.0b2, 2018.1.0b3, 2018.1.0b5, 2018.1.0b6, 2018.1.0b9, 2018.2.0a2
Works Fine On: 2018.1.0b1, 2018.1.0a7

Notes:
- Appears always.
- Appears on both Mac and Windows.
- Editor sometimes even crashes once the project is loaded again after the force quit.
- Bug Reporter was not poped-up.

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