fix getHighlightLayerByName no null check
fix getHighlightLayerByName no null check

BabylonJS/Babylon.js,RaananW/Babylon.js,BabylonJS/Babylon.js,RaananW/Babylon.js,BabylonJS/Babylon.js,sebavan/Babylon.js,sebavan/Babylon.js,RaananW/Babylon.js,sebavan/Babylon.js