Fix AVPlayer periodic time observers not being removed

Tusker/Screens/Gallery/VideoControlsViewController.swift

@@ -120,6 +120,15 @@ class VideoControlsViewController: UIViewController {
         fatalError("init(coder:) has not been implemented")
     }
     
+    deinit {
+        if let timestampObserverToken {
+            player.removeTimeObserver(timestampObserverToken)
+        }
+        if let scrubberObserverToken {
+            player.removeTimeObserver(scrubberObserverToken)
+        }
+    }
+    
     override func viewDidLoad() {
         super.viewDidLoad()