memory_limit = -1 causes error, fix included

If memory_limit is disabled (set to -1) the color module throws an error.

fix
color.module line 349

    $limit = ini_get('memory_limit');
    if ($limit != -1)
    {
        $limit = parse_size($limit);
    }
  if (($usage + $required > $limit) && ($limit != -1)) {
      drupal_set_message(t('There is not enough memory available to PHP to change this theme\'s color scheme. You need at least %size more. memory_limit is set to %limit. Check the <a href="@url">PHP documentation</a> for more information.', array('%size' => format_size($usage + $required - $limit),'%limit' => $limit ,'@url' => 'http://www.php.net/manual/ini.core.php#ini.sect.resource-limits')), 'error');
      return;
    }
  }

The error is parse_size() transforms -1 to 1 and $limit isn't checked if it's -1