exists() returnes wrong result for null and null list

[ReneSpronk]

Spec states:

define "ExistsIsTrue": exists { 1, 3, 5, 7 }
define "ExistsIsFalse": exists { }
define "ExistsIsAlsoFalse": exists { null }
define "ExistsIsAlsoAlsoFalse": exists null

CQL Runner returns 'undefined' (should be: false) for:

library BareMinimum version '0.0.1'
using FHIR version '4.0.1'
define N: [Basic]
define X: exists N // 'undefined'