Fix crash due to nested navigation controllers

Tusker/Screens/Utilities/SplitNavigationController.swift

@@ -67,6 +67,17 @@ class SplitNavigationController: UIViewController {
         if let rootViewController {
             rootNav.viewControllers = [rootViewController]
         }
+        
+        // add the child VCs here, rather than in viewDidLoad, because this VC is added to the UISplitViewController,
+        // it needs a UINavigationController to be this VC's first child, otherwise it will embed this VC inside
+        // yet another UINavigationController, which can then cause a crash when we try to embed a nav controller inside
+        // of ourself (because nested nav controllers are forbidden)
+        rootNav.willMove(toParent: self)
+        addChild(rootNav)
+        rootNav.didMove(toParent: self)
+        secondaryNav.willMove(toParent: self)
+        addChild(secondaryNav)
+        secondaryNav.didMove(toParent: self)
     }
     
     required init?(coder: NSCoder) {
@@ -76,10 +87,10 @@ class SplitNavigationController: UIViewController {
     override func viewDidLoad() {
         super.viewDidLoad()
         
-        embedChild(rootNav, layout: false)
-        embedChild(secondaryNav, layout: false)
         rootNav.view.translatesAutoresizingMaskIntoConstraints = false
+        view.addSubview(rootNav.view)
         secondaryNav.view.translatesAutoresizingMaskIntoConstraints = false
+        view.addSubview(secondaryNav.view)
 
         separatorView.backgroundColor = .separator
         separatorView.translatesAutoresizingMaskIntoConstraints = false