title: EXC_BREAKPOINT 0x00000000e7ffdefe in Crashlytics
body: <p>I'm getting the following error in Crashlytics</p>
  
  <blockquote>
    <p>LoginViewController.swift line 277
    LoginViewController.textField(UITextField,
    shouldChangeCharactersInRange : _NSRange, replacementString : String)
    -> Bool</p>
  </blockquote>
  
  <p>There's the code in my project: </p>
  
  <pre><code>   // MARK: - UITextFieldDelegate
  func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -&gt; Bool {
      if textField == txtSearch &amp;&amp; string != "\n"{
          var substring: String = textField.text!
          substring = (substring as NSString).stringByReplacingCharactersInRange(range, withString: string)
          self.searchAutocompleteEntriesWithSubstring(substring)
      }
      return true;
  }
  </code></pre>
  
  <p>This error ocurrs only sometimes</p>