iphone program received signal:"SIGABRT"

C/C++ code

UITabBarController *tabBarController =      (UITabBarController *)self.window.rootViewController;      UINavigationController *navigationController =      [[tabBarController viewControllers] objectAtIndex:0];      PlayerViewController *playerViewController =      [[navigationController viewControllers] objectAtIndex:0];    playerViewController.players = players;      return YES;

用的Stroryboard
TabBar->Nav(包含TableView)

照着示例写的，可是运行报错。
报错：iphone program received signal:"SIGABRT"
位置：
PlayerViewController *playerViewController =
[[navigationController viewControllers] objectAtIndex:0];

[解决办法]
看下[navigationController viewControllers] 返回的NSArray 中的object数量是不是0 或者是nil