fix(lazyLoad): fixed getting parent injector in angular 4.2

Author: aitboudad

src/lazyLoad/lazyLoadNgModule.ts

@@ -133,7 +133,7 @@ export function loadModuleFactory(moduleToLoad: NgModuleToLoad, ng2Injector: Inj
  */
 export function applyNgModule(transition: Transition, ng2Module: NgModuleRef<any>): LazyLoadResult {
   let injector = ng2Module.injector;
-  let parentInjector = <Injector> ng2Module.injector['parent'];
+  let parentInjector = <Injector> ng2Module.injector['parent'] || ng2Module.injector['_parent'];
   let uiRouter: UIRouter = injector.get(UIRouter);
   let registry = uiRouter.stateRegistry;
 
@@ -193,4 +193,4 @@ export function multiProviderParentChildDelta(parent: Injector, child: Injector,
   let childVals: RootModule[] = child.get(token, []);
   let parentVals: RootModule[] = parent.get(token, []);
   return childVals.filter(val => parentVals.indexOf(val) === -1);
-}
+}