In a case about a “tip pool” and a restaurant’s alleged practice of withholding taxes on phantom income, Gustavo Perez sued Over-Easy Inc. for allegedly violating the Fair Labor Standards Act.As a waiter at Over-Easy’s restaurant, La Scarola, in Chicago’s River West neighborhood, Perez had to give 10 percent of his tips to the bartender and 20 percent to the busboys. But the income tax withholdings for the paychecks La Scarola gave to servers were allegedly based on the entire amount of the …