Repro steps:

1. Open Scene1 from the attached project.
2. Drag the AssignMe material from the project window onto the particle system
3. Observe glitch

Notes:
- not a regression, happens in 2018.1, where the feature was introduced.

RichardK note:
- i think we can fix it by hooking into the SetDirty call on the SetMaterial. either make it virtual and override it, or hook into whatever it causes to be called (was it UpdateRenderer or something?)
- basically we need to reset the vertex streams hash to 0, to forceit to be recalculated, whenever the material changes.