如何在iPhone上HTTP连接失败时弹出警报？

我想编写一些代码来处理HTTP连接失败时的异常.我使用以下代码:

-(void) connection:(NSURLConnection *)connection
  didFailWithError: (NSError *)error {
    UIAlertView *errorAlert = [[UIAlertView alloc]
                    initWithTitle: [error localizedDescription]
                    message: [error localizedFailureReason]
                    delegate:nil
                    cancelButtonTitle:@"OK"
                    otherButtonTitles:nil];
    [errorAlert show];
    [errorAlert release];
    [activityIndicator stopAnimating];
    NSLog (@"Connection Failed with Error");
}

但是当连接失败时程序崩溃了.如何在没有程序崩溃的情况下弹出警报？