我正在与iAd发生冲突，说它在转换过程中无法呈现模态视图控制器。有什么办法解决这个问题？我无法控制iAd如何呈现视图控制器以响应敲击...
崩溃日志：
http://crashes.to/s/8454c6d34cf
Fatal Exception NSInternalInconsistencyException
Attempting to begin a modal transition from <UINavigationController: 0x15e2cd80> to <_ADRemoteViewController: 0x171d58d0> while a transition is already in progress. Wait for viewDidAppear/viewDidDisappear to know the current transition has completed
0 ... CoreFoundation __exceptionPreprocess + 130
1 libobjc.A.dylib objc_exception_throw + 38
2 CoreFoundation +[NSException raise:format:]
3 Foundation -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 90
4 UIKit -[UIWindowController transition:fromViewController:toViewController:target:didEndSelector:animation:] + 244
5 UIKit -[UIViewController presentViewController:withTransition:completion:] + 4668
6 iAd -[ADAdSpace _considerPresentingActionViewController] + 1642
7 ... libdispatch.dylib _dispatch_call_block_and_release + 10
8 libdispatch.dylib _dispatch_client_callout + 22
9 libdispatch.dylib _dispatch_main_queue_callback_4CF$VARIANT$mp + 268
10 CoreFoundation __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 8
11 CoreFoundation __CFRunLoopRun + 1300
12 CoreFoundation CFRunLoopRunSpecific + 522
13 CoreFoundation CFRunLoopRunInMode + 106
14 GraphicsServices GSEventRunModal + 138
15 UIKit UIApplicationMain + 1136
16 YouDoodle
AppDelegate.m line 158
main
17 YouDoodle start + 16888