Actions brought under this article shall have precedence over all other actions, excepting criminal proceedings, election contests and hearings on injunctions. If a complaint is filed under this article by a citizen, it shall not be dismissed by the plaintiff or for want of prosecution except upon a sworn statement made by the complainant and his attorney, setting forth the reasons why the action should be dismissed, and the dismissal ordered by the court. In case of failure to prosecute any such action with reasonable diligence, or at the request of the plaintiff, the court, in its discretion, may substitute any other citizen consenting thereto for the plaintiff. If the action is brought by a citizen and the court finds there was no reasonable ground or cause therefor, the costs shall be taxed against such citizen.