check for null id when loading cubemaps (#2137)
check for null id when loading cubemaps (#2137)


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