Incorrect result for Collapse

[brynrhodes]

The "TestCollapseNull" test case is:

collapse { Interval(null, null) }

According to the spec though, the result of this should be { Interval(null, null) }, based on this line:

"if the input list contains a single interval, the result is a list with that interval"

More broadly, the expression Interval(null, null) actually results in a null, rather than in an interval with null boundaries.

[brynrhodes]

Withdrawing this, down a rabbit hole