Fixed Room:onHumanoidLeave()'s callForStaff() condition

Staff will now always be called to use a room when a staff member
leaves before a patient has finished using the room. Before this
commit staff wouldn't be called if the room didn't have a queue.
Merge pull request #315 from J-Shep/fixedCallForStaffBug

Fixed Room:onHumanoidLeave()'s callForStaff() condition