don't call model.destroy twice when unloading
don't call model.destroy twice when unloading

sereepap2029/playcanvas,playcanvas/engine,H1Gdev/engine,sereepap2029/playcanvas,playcanvas/engine,aidinabedi/playcanvas-engine,guycalledfrank/engine,aidinabedi/playcanvas-engine,guycalledfrank/engine,sereepap2029/playcanvas,MicroWorldwide/PlayCanvas,H1Gdev/engine,MicroWorldwide/PlayCanvas