How to reproduce:
1. Open Unity
2. Load user-submitted project(Demo_Unity.zip)
3. Open 'Extended_Snow_Scene.unity' scene
4. Select 'Extended_Snow_Material.mat'
5. Change either 'Level of snow' or 'Snow depth' properties

Extended reproduction steps:
1. Open Unity
2. Load user-submitted project(Demo_Unity.zip)
3. Open 'Extended_Snow_Scene.unity' scene
4. Edit 'Extended_Snow_Effect.shader' vertex function(preferably where 'Level of snow' or 'Snow depth' properties are used)
5. Select 'Extended_Snow_Material.mat'
6. Change either 'Level of snow' or 'Snow depth' properties

(Unity doesn't crash if the shader has been edited after Unity Editor startup)

7. Close Unity and open the same project and scene again
8. Select 'Extended_Snow_Material.mat'
9. Change either 'Level of snow' or 'Snow depth' properties

Expected result: Unity applies new property values to shader results
Actual result: Unity crashes indicating that an error occurred while finding material properties

Reproducible with - 2017.1.0a1, 2017.1.3f1, 2017.2.1p1, 2017.3.0p1, 2018.1.0b1
Not reproducible with - 5.6.5f1