Doing any kind of offscreen rendering (involving particle systems) from within OnWillRenderObject causes billboard particles to orient to that offscreen camera even for the main (outer) camera.

Repro steps:
1. Open scene from attached project.
2. Press play.
3. Observe wrong orientation of particles.

Expected outcome: particles to billboard properly.

Notes:
- not a regression; using new particle features not available in 5.3
- reproducible back in 5.4.0b1, not reproducible in 5.4.0a2