我添加了一个新的初始UIViewController后，UINavigationController“表现得很疯狂”

I had a UINavigationController set as initial view controller. The root view controller for that navigation controller shows a menu where users can see product categories (In case that's interesting for anyone :)). The root view controller loads JSON data from an URL, so it takes a little while until the view shows up (which is fine). That data will be use in all the app, so it's an important step.I had a UINavigationController set as initial v