ObjectLoader: Rescued castShadow/receiveShadow. See #6282.

src/loaders/ObjectLoader.js

@@ -524,6 +524,9 @@ THREE.ObjectLoader.prototype = {
 
 			}
 
+			if ( data.castShadow !== undefined ) object.castShadow = data.castShadow;
+			if ( data.receiveShadow !== undefined ) object.receiveShadow = data.receiveShadow;
+
 			if ( data.visible !== undefined ) object.visible = data.visible;
 			if ( data.userData !== undefined ) object.userData = data.userData;