title: performSegueWithIdentifier: causes app to crash
body: <p>I have a button that is pressed after user enters email information. I have an alert view that is displayed when there is no email entered but if there is I want the button to segue to another view controller.</p>
  
  <p>The following code causes my app to crash. I have no idea why. Please help.</p>
  
  <p>(note: I have tried "sender:self]" "sender:nil]" and "sender:sender]" and they all make my app crash.)  </p>
  
  <pre><code>- (IBAction)nextButtonPushed:(id)sender {
  
      if ([self.emailTextField.text  isEqual: @""]) {
  
          emailAlertView = [[UIAlertView alloc] initWithTitle:@"Missing Email" message:@"A destination email is required to send." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
          [emailAlertView show];
          self.nextButton.enabled = NO;
      }
  
      else {
  
          eString = self.eTextField.text;
          hString = self.hField.text;
          emailAddress = self.emailTextField.text;
  
          [userDefaults setObject:eString forKey:@"e"];
  
          [userDefaults setObject:hString forKey:@"h"];
  
          [userDefaults setObject:emailAddress forKey:@"email"];
  
          [self performSegueWithIdentifier:@"next" sender:self];
      }
  
  }
  </code></pre>