give morph target a default name when its missing from the glb (#2028)
give morph target a default name when its missing from the glb (#2028)

Co-authored-by: Donovan Hutchence <206e9a39e6db29de606a97e8caefd40a0b429916@snapchat.com>
aidinabedi/playcanvas-engine,sereepap2029/playcanvas,sereepap2029/playcanvas,aidinabedi/playcanvas-engine,playcanvas/engine,MicroWorldwide/PlayCanvas,playcanvas/engine,MicroWorldwide/PlayCanvas,sereepap2029/playcanvas