code: @Override
    public final org.jdom2.Element addContent(String text) {
      // ignore empty elements
      if (text == null) {
        return null;
      }
      return super.addContent(cleanUpString(text));
    }
docs: This adds text content to this element. It does not replace the existing content as does setText().
  @param text String to add. Null values are ignored.
  @return This element modified