June 12 (UPI) -- A cyberattack has crippled distribution channels for one of the nation's top organic food distributors, leading to empty shelves at grocery stores nationwide. Rhode-Island-based United Natural Foods Inc., a major supplier to Whole Foods, became aware of the attack on June 5th, a filing with the Securities and Exchange Commission said. UNFI said the breach affected its ability to fulfill customer orders. "It's affecting operations in a very, very significant way," an employee at