@Nullable
  public XExpression toXExpression() {
    checkConverted();
    // old versions may have empty expressions serialized
    if (StringUtil.isEmptyOrSpaces(myExpression)) {
      return null;
    }
    return new XExpressionImpl(XmlStringUtil.unescapeIllegalXmlChars(myExpression),
                               Language.findLanguageByID(myLanguage),
                               myCustomInfo,
                               myMode);
  }
@Nullable
  public XExpression toXExpression()