UIActivityViewController issue iOS 7 and iOS 8?

I’m building an article reading app for iPad. I have integrated a social sharing functionality which means user can share articles on Facebook, and google mail. I’m using UIActivityViewController for sharing.

There is a bar button item,when user click on that UIActivityViewController opens.I updated Xcode 6 When I run on simulator it runs fine But I run on real device(iPad) with iOS 7,the app get crash on clicking on bar button item. this is my code:

     - (IBAction)ysshareAction:(id)sender
       {

         NSURL *linkURL = [NSURL URLWithString:_DetailModal1[4]];//article url
         NSMutableAttributedString *stringText = [[NSMutableAttributedString alloc]  initWithString:_DetailModal1[0]];//_DetailModal1[0] contain article title////
        [stringText addAttribute:NSLinkAttributeName value:linkURL range:NSMakeRange(0, stringText.length)];
        NSArray * itemsArray = @[[NSString stringWithFormat:@"%@",_DetailModal1[0]], [NSURL URLWithString:_DetailModal1[4]]];
        NSArray * applicationActivities = nil;
        UIActivityViewController * AVC = [[UIActivityViewController alloc] initWithActivityItems:itemsArray applicationActivities:applicationActivities];
        AVC.popoverPresentationController.sourceView = _webView;
        [self presentViewController:AVC animated:YES completion:nil];
        [AVC setCompletionHandler:^(NSString *act, BOOL done)
        {

        if([act isEqualToString:UIActivityTypeMail]) {
         ServiceMsg = @"Mail sent!";
     } else if([act isEqualToString:UIActivityTypePostToTwitter]) {
         ServiceMsg = @"Article Shared!";
     } else if([act isEqualToString:UIActivityTypePostToFacebook]) {
         ServiceMsg = @"Article Shared!";
     } else if([act isEqualToString:UIActivityTypeMessage]) {
         ServiceMsg = @"SMS sent!";
     } else if([act isEqualToString:UIActivityTypeAddToReadingList]) {
         ServiceMsg = @"Added to Reading List";
     } else if([act isEqualToString:UIActivityTypeCopyToPasteboard]){
         ServiceMsg = @"Copied Link";
     }

     if ( done )
     {
         UIAlertView *Alert = [[UIAlertView alloc] initWithTitle:ServiceMsg message:@"" delegate:nil cancelButtonTitle:@"ok" otherButtonTitles:nil];
         [Alert show];

          }
       }];

    }

Help is appreciated!