title: UIWebView - crash when dismissing modal view controller while request is in progress
body: <p>Hey all,
  I am presenting a modal view controller and loading a webpage on that view controller in a UIWebView:</p>
  
  <pre><code>- (void)viewWillAppear:(BOOL)animated
  {
       self.requestObj = [NSURLRequest requestWithURL:[NSURL URLWithString:[MPServerPrefs serverPrefs].url_of_sandwich]];
       [self.helpWebView loadRequest:self.requestObj];
  }
  </code></pre>
  
  <p>Everything works fine if I let the webpage load and then dismiss the view. If I dismiss the view while the request is loading, I get this stacktrace:</p>
  
  <pre><code>#0  0x31a94466 in objc_msgSend
  #1  0x35ebcb70 in -[UIWebView webView:identifierForInitialRequest:fromDataSource:]
  #2  0x35ebc1c0 in -[UIWebViewWebViewDelegate webView:identifierForInitialRequest:fromDataSource:]
  #3  0x36130d04 in __invoking___
  #4  0x36130bd4 in -[NSInvocation invoke]
  #5  0x36130730 in -[NSInvocation invokeWithTarget:]
  #6  0x329fc2f4 in -[_WebSafeForwarder forwardInvocation:]
  </code></pre>
  
  <p>I did some searching and can't figure out what's going on. Any ideas? Do I need to cancel my request when dismissing the view controller?</p>
  
  <p>Many thanks!</p>