crash only with iPad (simulator or device) - [__NSArrayM insertObject:atIndex:]

I try to test an iPhone (not universal) app on an iPad (device and simulator), but I get this error:

2013-02-09 15:25:23.907 iFormularioNew_Free[5160:c07] CRASH: *** -[__NSArrayM insertObject:atIndex:]: object cannot be nil
2013-02-09 15:25:23.910 iFormularioNew_Free[5160:c07] Stack Trace: (
    0   CoreFoundation                      0x0204d02e __exceptionPreprocess + 206
    1   libobjc.A.dylib                     0x0151ee7e objc_exception_throw + 44
    2   CoreFoundation                      0x02000b6a -[__NSArrayM insertObject:atIndex:] + 314
    3   CoreFoundation                      0x02000a20 -[__NSArrayM addObject:] + 64
    4   UIKit                               0x00545894 -[UIViewController _addChildViewController:performHierarchyCheck:notifyWillMove:] + 344
    5   UIKit                               0x00553b8c -[UIViewController(UIContainerViewControllerProtectedMethods) addChildViewController:] + 68
    6   iFormularioNew_Free                 0x0003a27c -[BannerViewController loadView] + 348
    7   UIKit                               0x00543ff8 -[UIViewController loadViewIfRequired] + 73
    8   UIKit                               0x00544232 -[UIViewController view] + 33
    9   iFormularioNew_Free                 0x0003aa81 __63-[BannerViewController bannerView:didFailToReceiveAdWithError:]_block_invoke + 49
    10  UIKit                               0x004ae067 +[UIView(UIViewAnimationWithBlocks) _setupAnimationWithDuration:delay:view:options:animations:start:completion:] + 506
    11  UIKit                               0x004ae276 +[UIView(UIViewAnimationWithBlocks) animateWithDuration:animations:] + 99
    12  iFormularioNew_Free                 0x0003a9fb -[BannerViewController bannerView:didFailToReceiveAdWithError:] + 283
    13  iAd                                 0x00072d23 -[ADBannerView _sanitizeAndForwardErrorToDelegate:] + 254
    14  iAd                                 0x00072991 __28-[ADBannerView setDelegate:]_block_invoke_0 + 92
    15  iAd                                 0x00072916 -[ADBannerView setDelegate:] + 266
    16  iFormularioNew_Free                 0x0003a0ae -[BannerViewController initWithContentViewController:] + 382
    17  iFormularioNew_Free                 0x0000336e -[AppDelegate application:didFinishLaunchingWithOptions:] + 4718
    18  UIKit                               0x00460157 -[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 266
    19  UIKit                               0x00460747 -[UIApplication _callInitializationDelegatesForURL:payload:suspended:] + 1248
    20  UIKit                               0x0046194b -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 805
    21  UIKit                               0x00472cb5 -[UIApplication handleEvent:withNewEvent:] + 1022
    22  UIKit                               0x00473beb -[UIApplication sendEvent:] + 85
    23  UIKit                               0x00465698 _UIApplicationHandleEvent + 9874
    24  GraphicsServices                    0x0193adf9 _PurpleEventCallback + 339
    25  GraphicsServices                    0x0193aad0 PurpleEventCallback + 46
    26  CoreFoundation                      0x01fc2bf5 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 53
    27  CoreFoundation                      0x01fc2962 __CFRunLoopDoSource1 + 146
    28  CoreFoundation                      0x01ff3bb6 __CFRunLoopRun + 2118
    29  CoreFoundation                      0x01ff2f44 CFRunLoopRunSpecific + 276
    30  CoreFoundation                      0x01ff2e1b CFRunLoopRunInMode + 123
    31  UIKit                               0x0046117a -[UIApplication _run] + 774
    32  UIKit                               0x00462ffc UIApplicationMain + 1211
    33  iFormularioNew_Free                 0x0000202d main + 141
    34  iFormularioNew_Free                 0x00001f55 start + 53
)
2013-02-09 15:25:23.953 iFormularioNew_Free[5160:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil'
*** First throw call stack:
(0x204d012 0x151ee7e 0x2000b6a 0x2000a20 0x545894 0x553b8c 0x3a27c 0x543ff8 0x544232 0x3aa81 0x4ae067 0x4ae276 0x3a9fb 0x72d23 0x72991 0x72916 0x3a0ae 0x336e 0x460157 0x460747 0x46194b 0x472cb5 0x473beb 0x465698 0x193adf9 0x193aad0 0x1fc2bf5 0x1fc2962 0x1ff3bb6 0x1ff2f44 0x1ff2e1b 0x46117a 0x462ffc 0x202d 0x1f55)
libc++abi.dylib: terminate called throwing an exception

if I get iADSuite sample code and I change from universal to iphone and I test the application on an ipad (device o r simulator) I get the same error. Where is the problem?

EDIT: code:

here crash:

_bannerViewController = [[BannerViewController alloc] initWithContentViewController:self.tabBarController];
self.window.rootViewController = _bannerViewController;

BannerViewController.m

NSString * const BannerViewActionWillBegin = @"BannerViewActionWillBegin";
NSString * const BannerViewActionDidFinish = @"BannerViewActionDidFinish";

@interface BannerViewController () <ADBannerViewDelegate>

@end

@implementation BannerViewController {
    ADBannerView *_bannerView;
    UIViewController *_contentController;
}

- (instancetype)initWithContentViewController:(UIViewController *)contentController
{
    self = [super init];
    if (self != nil) {
        // On iOS 6 ADBannerView introduces a new initializer, use it when available.
        if ([ADBannerView instancesRespondToSelector:@selector(initWithAdType:)]) {
            _bannerView = [[ADBannerView alloc] initWithAdType:ADAdTypeBanner];
        } else {
            _bannerView = [[ADBannerView alloc] init];
        }
        _bannerView.delegate = self;
        _contentController = contentController;
    }
    return self;
}

- (void)loadView{
    UIView *contentView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    [contentView addSubview:_bannerView];
    [self addChildViewController:_contentController];
    [contentView addSubview:_contentController.view];
    [_contentController didMoveToParentViewController:self];
    self.view = contentView;
}

#if __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_6_0
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return [_contentController shouldAutorotateToInterfaceOrientation:interfaceOrientation];
}
#endif

- (UIInterfaceOrientation)preferredInterfaceOrientationForPresentation{
    return [_contentController preferredInterfaceOrientationForPresentation];
}

- (NSUInteger)supportedInterfaceOrientations{
    return [_contentController supportedInterfaceOrientations];
}

- (void)viewDidLayoutSubviews{
    CGRect contentFrame = self.view.bounds, bannerFrame = CGRectZero;
#if __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_6_0
    // If configured to support iOS <6.0, then we need to set the currentContentSizeIdentifier in order to resize the banner properly.
    // This continues to work on iOS 6.0, so we won't need to do anything further to resize the banner.
    if (contentFrame.size.width < contentFrame.size.height) {
        _bannerView.currentContentSizeIdentifier = ADBannerContentSizeIdentifierPortrait;
    } else {
        _bannerView.currentContentSizeIdentifier = ADBannerContentSizeIdentifierLandscape;
    }
    bannerFrame = _bannerView.frame;
#else
    // If configured to support iOS >= 6.0 only, then we want to avoid currentContentSizeIdentifier as it is deprecated.
    // Fortunately all we need to do is ask the banner for a size that fits into the layout area we are using.
    // At this point in this method contentFrame=self.view.bounds, so we'll use that size for the layout.
    bannerFrame.size = [_bannerView sizeThatFits:contentFrame.size];
#endif

    if (_bannerView.bannerLoaded) {
        contentFrame.size.height -= bannerFrame.size.height;
        bannerFrame.origin.y = contentFrame.size.height;
    } else {
        bannerFrame.origin.y = contentFrame.size.height;
    }
    _contentController.view.frame = contentFrame;
    _bannerView.frame = bannerFrame;
}
- (void)bannerViewDidLoadAd:(ADBannerView *)banner{
    [[NSNotificationCenter defaultCenter] postNotificationName:BannerViewActionWillBegin object:self];

    [UIView animateWithDuration:0.25 animations:^{
        [self.view setNeedsLayout];
        [self.view layoutIfNeeded];
    }];
}
- (void)bannerView:(ADBannerView *)banner didFailToReceiveAdWithError:(NSError *)error {
    [[NSNotificationCenter defaultCenter] postNotificationName:BannerViewActionDidFinish object:self];

    [UIView animateWithDuration:0.25 animations:^{
        [self.view setNeedsLayout];
        [self.view layoutIfNeeded];
    }];
}
- (BOOL)bannerViewActionShouldBegin:(ADBannerView *)banner willLeaveApplication:(BOOL)willLeave {
    return YES;
}
- (void)bannerViewActionDidFinish:(ADBannerView *)banner{}

I deleted my earlier answer and I am posting this new answer instead.

Look at the stack trace. The problem is due to calling:

_bannerView.delegate = self;

This results in a chain of calls that leads to the loadView method of BannerViewController being called while still in the middle of the initWithContentViewController: being executed. But at this point, the _contentController ivar isn't set yet.

Given that setting the delegate kicks off ad loads and the need for a view, the best solution is to wait and set the _bannerView.delegate in the viewDidLoad method.

Another solution is to reorder the calls in the initWithContentViewController: method to:

- (instancetype)initWithContentViewController:(UIViewController *)contentController {
    self = [super init];
    if (self != nil) {
        // This must be called before you set the delegate on _bannerView
        _contentController = contentController;

        // On iOS 6 ADBannerView introduces a new initializer, use it when available.
        if ([ADBannerView instancesRespondToSelector:@selector(initWithAdType:)]) {
            _bannerView = [[ADBannerView alloc] initWithAdType:ADAdTypeBanner];
        } else {
            _bannerView = [[ADBannerView alloc] init];
        }
        _bannerView.delegate = self;
    }

    return self;
}

Yet another solution would be to get rid of the loadView implementation and put all of that code (minus creating the content view) at the start of viewDidLoad.