当显示为模态视图控制器时，不能将其释放到UINavigationController堆栈中。

First: I ported my App to ARC and everything seemed to work. But now I discovered a problem: I have a UINavigationController that is presented modally with some UIViewControllers on its stack. But when I dismiss the modal view controller, the view controllers from the stack don't seem to be deallocated. Here is what I do:First: I ported my App to ARC and everything se