Cry.
Suddenly my app I'm working on doesn't work anymore -> I'm now getting the following crash when I start my app:
Objective-C exception thrown. Name: NSInternalInconsistencyException Reason: Application windows are expected to have a root view controller at the end of application launch
Now, I've read the Stable release notes which say this
[Upstream change] [iOS] iOS 9 has stricter requirements for setting a RootViewController. "Objective-C exception thrown. Name: NSInternalInconsistencyException Reason: Application windows are expected to have a root view controller at the end of application launch". Possible workaround: Set the Window.RootViewController property in the AppDelegate.FinishedLaunching() method. (See the troubleshooting guide for additional details.)
Ok . not good nor do I know why ...
Checking the guide for help .. it says this :
This is error is being raised because app Windows are expected to have a Root View Controller at the end of application launch and your existing app doesn't.
Setup RootViewController property of app Window in FinishedLaunching method in AppDelegate class to point to a View Controller in your app's UI.
Ok .. so I want to try this but I have no idea what View Controller should I use? In fact, I have no idea if i even have any!
I've only got a few classes which inherit from ContentPage. I've not manually made any View Controllers 
Can anyone help, please? It's very frustrating because I cannot run the simulator anymore to test my app!