Whenever, in any criminal case, the defendant shall be adjudged guilty and a punishment by fine or imprisonment shall be imposed in excess of that allowed by law, the judgment shall not for that reason alone be judged altogether void, nor be wholly reversed and annulled by any court of review, but the same shall be valid and effectual to the extent of the lawful penalty, and shall only be reversed or annulled on writ of error or otherwise, in respect to the unlawful excess.