[FIX] Avoid normalizing a zero length vector in particle vertex shader  (#1703)
[FIX] Avoid normalizing a zero length vector in particle vertex shader  (#1703)

* added preUpdateHook

* fix particle system bug

sereepap2029/playcanvas,aidinabedi/playcanvas-engine,sereepap2029/playcanvas,MicroWorldwide/PlayCanvas,playcanvas/engine,MicroWorldwide/PlayCanvas,playcanvas/engine,aidinabedi/playcanvas-engine,sereepap2029/playcanvas