*** Assertion failure in -[UIApplication _runWithMainScene:transitionContext iOS9.1闪退问题解决

错误原因在于 AppDelegate 中 didFinishLaunchingWithOptions 结束前 未定义 rootViewController，Xcode7规定必须要有rootViewController。
定义一个空UIViewController即可，添加如下代码解决：
UIViewController *emptyView = [[ UIViewController alloc ]initNibName:nil bundle:nil ];
self. window .rootViewController = emptyView;

确保 AppDelegate 中 didFinishLaunchingWithOptions  window定义 rootViewController