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; 

Stroryboard
useTabBar-> Nav (included TableView)

Shining example to write, but run error.
Error: iphone program received signal: "SIGABRT"
Location:
PlayerViewController * playerViewController =
[[NavigationController viewControllers] objectAtIndex: 0];
Reply:
Look [navigationController viewControllers] Returns the number of NSArray object is not 0 or nil