Unexpected nil window in _UIApplicationHandleEventFromQueueEvent

One of my old apps is not working with iOS8. When I start the app up, and try to tap on the screen anywhere, I get this message in my console:

unexpected nil window in _UIApplicationHandleEventFromQueueEvent, 
_windowServerHitTestWindow: <UIWindow: 0x7fe4d3e52660; frame = (0 0; 320 568); 
opaque = NO; autoresize = RM+BM; gestureRecognizers = <NSArray: 0x7fe4d3e2c450>; 
layer = <UIWindowLayer: 0x7fe4d3e86a10>>

I'm using an old style MainWindow.xib. In the MainWindow.xib is my Window object, as well as a UINavigationController which has its first View Controller defined within as well. The image below is showing the Outlets connected to the App Delegate.

The white "view" in the screenshot below is the UIWindow. The view on the right is the UINavigationController (nav bar hidden) with the first ViewController defined inside it.

How do I fix this without recreating the entire app from scratch with a new project?

EDIT: I just discovered there is a TINY strip wherein my buttons will actually receive their taps/clicks.

I've also noticed that my self.view.window is nil. How do I make sure that is set?

Additional to B H answer. Also look this answer.

Got this issue when launching my landscape only app from portrait orientation (also the app shouldn't be presented in recently opened apps list, which can be seen by pressing Home button twice. Perhaps, iOS somehow caches the orientation and window size).

My code was

self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
[self.window makeKeyAndVisible];

I set W+H autoresizing mask for window, it didn't help me, because the window don't being resized on rotation, but the transform matrix is changed.

The solution is simple

self.window = [UIWindow new];
[self.window makeKeyAndVisible];
self.window.frame = [[UIScreen mainScreen] bounds];

So the frame is set AFTER the window get its orientation from root view controller.