修复因 interactivePopGestureRecognizer?.delegate 丢失造成应用可能卡住的问题

ruby-china-ios/Controllers/TopicDetailsViewController.swift

@@ -14,7 +14,7 @@ class TopicDetailsViewController: WebViewController {
     fileprivate var followButton: UIButton!
     fileprivate var likeButton: UIButton!
     fileprivate var favorited: Bool = false
-
+    fileprivate var interactivePopDelegate: UIGestureRecognizerDelegate?
 
     convenience init(topicID: Int, topicPath: String? = nil) {
         self.init(path: topicPath ?? "/topics/\(topicID)")
@@ -33,13 +33,15 @@ class TopicDetailsViewController: WebViewController {
         super.viewWillAppear(animated)
         navigationController?.setNavigationBarHidden(true, animated: animated)
         navigationController?.setToolbarHidden(false, animated: animated)
+        interactivePopDelegate = navigationController?.interactivePopGestureRecognizer?.delegate
         navigationController?.interactivePopGestureRecognizer?.delegate = nil
     }
 
     override func viewWillDisappear(_ animated: Bool) {
         super.viewDidAppear(animated)
         navigationController?.setNavigationBarHidden(false, animated: animated)
         navigationController?.setToolbarHidden(true, animated: animated)
+        navigationController?.interactivePopGestureRecognizer?.delegate = interactivePopDelegate
     }
 
     func setToolbars() {