Whenever improvements have been made on state-owned tidelands, shorelands, or beds of navigable waters, in front of cities or towns, prior to the location of harbor lines in front of the cities or towns, and the reserved harbor area as located include the improvements, no seizure or sale of the improvements for taxes shall be had until six months after the lands have been leased or offered for lease. However, this section shall not affect or impair the lien for taxes on the improvements.