It was bound to happen: A homeowner has filed suit against online realty giant Zillow, claiming the company’s controversial “Zestimate” tool repeatedly undervalued her house, creating a “tremendous road block” to its sale. The suit, which may be the first of its kind, was filed in Cook County Circuit Court by a Glenview, Ill., real estate lawyer, Barbara Andersen. The suit alleges that despite Zillow’s denial that Zestimates constitute …