Fix swipe back freezing the screen occasionally (#65)

Author: davdroman

Sources/NavigationTransitions/NavigationTransition+UIKit.swift

@@ -141,7 +141,11 @@ extension UINavigationController {
 			defaultDelegate = delegate
 		}
 
-		customDelegate = NavigationTransitionDelegate(transition: transition, baseDelegate: defaultDelegate)
+        if customDelegate == nil {
+            customDelegate = NavigationTransitionDelegate(transition: transition, baseDelegate: defaultDelegate)
+        } else {
+            customDelegate.transition = transition
+        }
 
 		#if !os(tvOS)
 		if defaultEdgePanRecognizer.strongDelegate == nil {

Sources/NavigationTransitions/NavigationTransitionDelegate.swift

@@ -4,7 +4,7 @@
 import UIKit
 
 final class NavigationTransitionDelegate: NSObject, UINavigationControllerDelegate {
-	let transition: AnyNavigationTransition
+	var transition: AnyNavigationTransition
 	private weak var baseDelegate: UINavigationControllerDelegate?
 	var interactionController: UIPercentDrivenInteractiveTransition?
 	private var initialAreAnimationsEnabled = UIView.areAnimationsEnabled