NaN is not in correct order in order by clause

[mstevan]

@mstevan
test-set: prod/EmptyOrderDecl.xml
test-cases: emptyorderdecl-16, 17, 20, 21, 23, 29

@team
NaN is not in correct order in order by clause. Check expected output for more details, but in ascending it should come before all these numbers and in descending it should be the other way around

Input:
declare default order empty least; for $i in (1,4,0 div 0E0,7) order by $i ascending return $i

Output:
1 4 7 NaN

Expected output:
NaN 1 4 7

[mstevan]

All tests are passing. At the moment, there are no other tests crashing because of fix