While developing iOS application in Xcode 11 I've changed deployment target to iOS 12. So all this code with SceneDelegate and scene sessions that is for new multi-window support is now unavailable. So I've commented it out totally.
But no I have such bug
There is no scene delegate set. A scene delegate class must be specified to use a main storyboard file.
And when I try to access self.window!.rootViewController to attach some initial UIViewController (it is also defined in Main.storyboard with isInitial attribute checked)