Black bar appears under navigation bar

It appeared as translucent property of UINavigationBar appeared to be messed up with frame other view controllers.

I would recommend following approach.

Create a base view controller from which other view controllers will inherit as follows,

#import "BaseViewController.h"

@interface BaseViewController ()

@end

@implementation BaseViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.navigationController.navigationBar.translucent = NO;
}

other view controllers will inherit above BaseViewController

// interface

#import <UIKit/UIKit.h>
#import "BaseViewController.h"

@interface ViewController : BaseViewController

@end

// implementation

#import "ViewController.h"

@implementation ViewController

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    // Here translucent property is enabled when the view is about to be disappeared.
    // However note that, translucent property needs to be enabled only on those view controllers which has prompt set on their navigation items.
    self.navigationController.navigationBar.translucent = YES;
}

Other view controllers without prompt implementation will work as usual however they also needs to inherit from BaseViewController.

Late answer but I stumbled across this problem today and found your question and it doesn't have an accepted answer yet.

I got this error while going from a prompted viewController to a non prompted viewController in storyboard.

I got that black bar just like you.

And to fix:

// In prompted vc
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    UIView.setAnimationsEnabled(false)
    self.navigationItem.prompt = nil
    UIView.setAnimationsEnabled(true)
}

This will remove the prompt instantly before switching viewcontroller.

UPDATE

func prompt() -> String? {
    return nil
}

override func viewWillAppear(animated: Bool) {
    let action = { self.navigationItem.prompt = self.prompt() }
    
    if self.navigationController?.viewControllers.count <= 1 {
        UIView.performWithoutAnimation(action)
    }
    else {
        action()
    }
}

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {        
    UIView.performWithoutAnimation {
        self.navigationItem.prompt = (segue.destinationViewController as? ViewController)?.prompt()
    }
}

The best way to solve this issue is setting the background of the window during push i.e,

let appdelegate = UIApplication.shared.delegate as! AppDelegate
appdelegate.window?.backgroundColor = UIColor.white