Nonexistent parameter in WebTestBase::assertNoLink()

Must have been a copy & paste issue. The parameter $index at assertNoLink() is not part of the method's signature:

  /**
   * Passes if a link with the specified label is not found.
   *
   * @param $label
   *   Text between the anchor tags.
   * @param $index
   *   Link position counting from zero.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE if the assertion succeeded, FALSE otherwise.
   */
  protected function assertNoLink($label, $message = '', $group = 'Other') {