Bug Reports • [2.1 alpha8] Question re Array.Pop() and unset?

CODE:

a := [10,,30]
b := [20,,40]
c := [30,,]
d := [,,5]
a.Default := 99
a3 := a.Pop(),  a2 := a.Pop()
b3 := b.Pop(),  b2 := b.Pop()
MsgBox(''
  . 'a2 is set: ' IsSet(a2) '`n'  ; 1
  . 'a2 type: ' type(a2) '`n'     ; String
  . 'a2 val: ' a2 '`n'            ; ''
  . 'b2 is set: ' IsSet(b2) '`n'  ; 1
  . 'b2 type: ' type(b2) '`n'     ; String
  . 'b2 val: ' b2 '`n'            ; ''
  . 'c length: ' c.Length '`n'    ; 1
  . 'd length: ' d.Length '`n'    ; 3
)