page_cache conflicts with CAPTCHA module

The value of $conf['cache'] should be considered.
If set to FALSE, beautify_set_cache() should not be called.

The CAPTCHA module disables page_cache, otherwise
the CAPTCHA jpg-image won't be regenerated and causes
a broken link.

function beautify_router($input) {
  $processor = variable_get('beautify_method', 'builtin');
  $mode = variable_get('beautify_mode', 2);
  switch ($processor) {
    case 'builtin':
      $output = beautify_process($input, $mode);
      break;
    case 'htmlawed':
      $output = beautify_htmlawed_process($input);
      break;
    case 'htmltidy':
      $output = beautify_htmltidy_process($input);
      break;
  }
>>>
  global $conf;
  if ( $conf['cache'] ) {
     beautify_set_cache($output);
  }
<<<
  print $output;
}