iOS: Fix runtime error in AppRTCMobile

webrtc/examples/objc/AppRTCMobile/ios/ARDVideoCallViewController.m

 /*
  *  Copyright 2015 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 107 matching lines @@
 - (void)appClient:(ARDAppClient *)client
       didGetStats:(NSArray *)stats {
   _videoCallView.statsView.stats = stats;
   [_videoCallView setNeedsLayout];
 }
 
 - (void)appClient:(ARDAppClient *)client
          didError:(NSError *)error {
   NSString *message =
       [NSString stringWithFormat:@"%@", error.localizedDescription];
+  [self hangup];
   [self showAlertWithMessage:message];
-  [self hangup];
 }
 
 #pragma mark - ARDVideoCallViewDelegate
 
 - (void)videoCallViewDidHangup:(ARDVideoCallView *)view {
   [self hangup];
 }
 
 - (void)videoCallViewDidSwitchCamera:(ARDVideoCallView *)view {
   // TODO(tkchin): Rate limit this so you can't tap continously on it.
@@ skipping 72 matching lines @@
   UIAlertAction *defaultAction = [UIAlertAction actionWithTitle:@"OK"
                                                           style:UIAlertActionStyleDefault
                                                         handler:^(UIAlertAction *action){
                                                         }];
 
   [alert addAction:defaultAction];
   [self presentViewController:alert animated:YES completion:nil];
 }
 
 @end