In any suit brought pursuant to the Political Subdivisions Tort Claims Act and sections 16-727, 16-728, 23-175, 39-809, and 79-610 and based upon an alleged defect in the construction or maintenance of a sidewalk, public building, or other public facility, an affirmative showing that the claimant had actual knowledge of the alleged defect at the time of the occurrence of the injury, and that an alternate safe route was available and known to the claimant, shall constitute a defense to the suit.