NEW YORK (Reuters) - Handheld computer shipments slumped in 2002, as an expected boom in demand from corporations failed to materialize, according to an industry study released on Monday. Worldwide shipments of personal digital assistants, or PDAs, the pocket-sized digital companions that can store thousands of appointments, contacts and notes, fell 9.1 percent to 12.1 million units in 2002, according to Dataquest Inc., a unit of research firm Gartner Inc. "The more lucrative enterprise market has been stagnant because of poor economic conditions and a perception that PDAs are not yet capable of delivering sufficient return on investment," said Todd...