Fixed BufferGeometryLoader breakage.

src/loaders/BufferGeometryLoader.js

@@ -60,7 +60,7 @@ THREE.BufferGeometryLoader.prototype = {
 		if ( boundingSphere !== undefined ) {
 
 			geometry.boundingSphere = new THREE.Sphere(
-				new THREE.Vector3().fromArray( boundingSphere.center ),
+				new THREE.Vector3().fromArray( boundingSphere.center !== undefined ? boundingSphere.center : [ 0, 0, 0 ] ),
 				boundingSphere.radius
 			);