Use existing isViewLoaded var

Defined in UIKit, this will actually already do what we need without
having to define a new var

// FREEBIE

Signal/src/ViewControllers/CallViewController.swift

@@ -25,7 +25,6 @@ class CallViewController: OWSViewController, CallObserver, CallServiceObserver,
 
     // MARK: Views
 
-    var isViewLoaded = false
     var hasConstraints = false
     var blurView: UIVisualEffectView!
     var dateFormatter: DateFormatter?
@@ -181,11 +180,14 @@ class CallViewController: OWSViewController, CallObserver, CallServiceObserver,
         updateCallUI(callState: call.state)
     }
 
+    override func loadView() {
+        self.view = UIView()
+        createViews()
+    }
+
     override func viewDidLoad() {
         super.viewDidLoad()
 
-        createViews()
-
         contactNameLabel.text = contactsManager.displayName(forPhoneIdentifier: thread.contactIdentifier())
         updateAvatarImage()
         NotificationCenter.default.addObserver(forName: .OWSContactsManagerSignalAccountsDidChange, object: nil, queue: nil) { [weak self] _ in
@@ -198,7 +200,6 @@ class CallViewController: OWSViewController, CallObserver, CallServiceObserver,
         call.addObserverAndSyncState(observer: self)
 
         Environment.getCurrent().callService.addObserverAndSyncState(observer: self)
-        self.isViewLoaded = true
     }
 
     // MARK: - Create Views