add workaround for invalid rawModel entries

seems to be connections with null relationships

examples/js/loaders/FBXLoader.js

@@ -2491,6 +2491,11 @@ THREE.FBXLoader = ( function () {
 									if ( modelID !== undefined ) {
 
 										var rawModel = fbxTree.Objects.Model[ modelID.toString() ];
+										
+										if (!rawModel) {
+											console.log("invalid rawModel", modelID, child);
+											return;
+										}
 
 										var node = {