DataSet.get([undefined]) returns [null], should return [] instead

The documentations says:

When no item is found, null is returned when a single item was requested, and and empty Array is returned in case of multiple id's.

But that's not the case, reading the code at https://github.com/almende/vis/blob/master/lib/DataSet.js#L373 it pushes item to the array no matter what is found.