How to reproduce:
1. Open the attached "TerrainVFX.zip" project
2. Open "New Scene", create a VFX Graph and add it to the scene
3. Enter Play mode and notice that the VFX particles are being rendered
4. Select "Terrain" in the Hierarchy, and enable "Draw Instanced" in the Terrain component
5. Enter Play mode again

Expected results: The VFX particles are still being rendered
Actual results: The VFX particles are no longer rendered

Reproducible with: 2019.3.0f2, 2020.1.0a16 (VFX Graph 7.1.6)
Not reproducible with: 2019.2.16f1 (VFX Graph 6.9.2)

Not reproducible:
1. with Multi Pass rendering mode
2. when the Terrain is completely flat