A Queens hospital has avoided a potentially disastrous strike after hammering out an 11th-hour deal with its nurses. Negotiations between staffers and Flushing Hospital Medical Center's sponsor, MediSys, came to a head last month when the nurses issued a 10-day strike warning after their health and pension benefits expired Dec. 31. Historically, management has issued temporary contract extensions throughout negotiations, though that courtesy was not extended to employees this time, union officials said. The walk out was set for Tuesday.