[FIX] Support loading models from URI if the mapping file is empty
[FIX] Support loading models from URI if the mapping file is empty

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