title: BAD ACCESS Error when using requestAccessToEntityType
body: <p>I am getting a EXEC_BAD_ACCESS Error when I attempt to run this code, and the user has not allowed access to the calendar. Does requestAccessToEntityType run on a separate thread, if thats the case how do I access the main thread to display the UIAlertView?</p>
  
  <pre><code>EKEventStore *store = [[EKEventStore alloc] init];
  if ([store respondsToSelector:@selector(requestAccessToEntityType:completion:)])
  {
      [store requestAccessToEntityType:EKEntityTypeEvent completion:^(BOOL granted, NSError *error)
       {
           if ( granted )
           {
               [self readEvents];
           }
           else
           {
               UIAlertView *alert = [[UIAlertView alloc] 
                                        initWithTitle:@"Denied Access To Calendar" 
                                        message:@"Access was denied to the calendar, please go into settings and allow this app access to the calendar!" 
                                        delegate:nil 
                                        cancelButtonTitle:@"Ok" 
                                        otherButtonTitles:nil, 
                                        nil];
               [alert show];
           }
       }];
  }
  </code></pre>