iphone program received signal:"SIGABRT"

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