No judgment shall hereafter be rendered by any court against any such county in any action brought to recover for any article, public improvement, material, service or labor contracted for or ordered in contravention of any statutory limitation, or when there are or were no funds legally available at the time, with which to pay for the same, or in the absence of a statute expressly authorizing such contract; Provided, that this section and sections 23-336 and 23-337 may not prevent the repairing of any bridge damaged by sudden casualty, when the county board shall first declare that an emergency exists, and give notice of its intention to repair such damage by at least one publication in some newspaper of general circulation in the county.