Unless an ordinance shall expressly provide to the contrary, if any portion of an ordinance or the application thereof to any person or circumstances shall be found to be invalid by a court of competent jurisdiction, such invalidity shall not affect the remaining portions or applications of the ordinance that can be given effect without the invalid portion or application; provided such remaining portions or applications are not determined by the court to be inoperable, and to this end ordinances are declared to be severable.