Show alert when user tries to activate local video without camera permissions.

// FREEBIE

Signal/src/call/CallService.swift

@@ -795,8 +795,9 @@ protocol CallServiceObserver: class {
             break
         }
 
-        // TODO: We could also check this whenever the app returns from the background,
-        //       since the user could disable this priviledge at all times.
+        // We don't need to worry about the user granting or remotinv this permission
+        // during a call while the app is in the background, because changing this
+        // permission kills the app.
         if authStatus != .authorized {
             DispatchQueue.main.async {
                 let title = NSLocalizedString("CAMERA_PERMISSION_MISSING_TITLE", comment: "Alert title when camera is not authorized")

Signal/src/view controllers/CallViewController.swift

@@ -662,8 +662,6 @@ class CallViewController: UIViewController, CallObserver, CallServiceObserver, R
     func didPressVideo(sender: UIButton) {
         Logger.info("\(TAG) called \(#function)")
         let hasLocalVideo = !sender.isSelected
-        audioModeVideoButton.isSelected = hasLocalVideo
-        videoModeVideoButton.isSelected = hasLocalVideo
         if let call = self.call {
             callUIAdapter.setHasLocalVideo(call: call, hasLocalVideo: hasLocalVideo)
         } else {