Fix broken animations (#106)

Author: davdroman

Sources/NavigationTransitions/NavigationTransitionDelegate.swift

@@ -7,22 +7,27 @@ final class NavigationTransitionDelegate: NSObject, UINavigationControllerDelega
 	var transition: AnyNavigationTransition
 	private weak var baseDelegate: UINavigationControllerDelegate?
 	var interactionController: UIPercentDrivenInteractiveTransition?
-	private var initialAreAnimationsEnabled = UIView.areAnimationsEnabled
+	private var initialAreAnimationsEnabled: Bool?
 
 	init(transition: AnyNavigationTransition, baseDelegate: UINavigationControllerDelegate?) {
 		self.transition = transition
 		self.baseDelegate = baseDelegate
 	}
 
 	func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool) {
-		initialAreAnimationsEnabled = UIView.areAnimationsEnabled
-		UIView.setAnimationsEnabled(transition.animation != nil)
+		if navigationController.transitionCoordinator != nil {
+			self.initialAreAnimationsEnabled = UIView.areAnimationsEnabled
+			UIView.setAnimationsEnabled(transition.animation != nil)
+		}
 		baseDelegate?.navigationController?(navigationController, willShow: viewController, animated: animated)
 	}
 
 	func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
 		baseDelegate?.navigationController?(navigationController, didShow: viewController, animated: animated)
-		UIView.setAnimationsEnabled(initialAreAnimationsEnabled)
+		if let initialAreAnimationsEnabled {
+			UIView.setAnimationsEnabled(initialAreAnimationsEnabled)
+			self.initialAreAnimationsEnabled = nil
+		}
 	}
 
 	func navigationController(_ navigationController: UINavigationController, interactionControllerFor animationController: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {