Employees at a Massachusetts health care company didn't get any invites to a holiday dinner dance this year. Over the past five years, it seems, fewer than half of the workers at Fallon Community Health Plan have shown up to the annual bash. So this year the CEO called it off. Instead, he left his employees a pre-recorded voicemail — giving them the day off. The company says closing for one day will actually cost more than the $30,000 or so it costs to hold the party. But it says extra time is the best holiday gift the company can offer its employees.