Setting particle system's Render Mode to Mesh (in Renderer module) causes artifacts. Other modes work fine, but switching to them from Mesh mode causes strange particle system behaviour.

The bug is a regression that is already fixed in the latest version.

To reproduce:
1. Create a new project.
2. Add a particle system into the scene
3. Set it's render mode to Mesh.
4. Set it back to one of the Billboard modes.

Desired outcome: Particle system is rendered properly.
Actual result: Particle system has strange flickering.

Reproduced using Windows 10 Pro on 5.5.2p2, 5.6.0b3, 5.6.0b11. Bug was on version 5.6.0b3.