[plt-scheme] finder:common-get-file-list

Hi, I'm trying to use the Framework (to select a folder), but I'm
having trouble getting the args right; I think I'm doing the minimum
sufficient to get a 'select files' dialog, but I'm getting a contrat
error that I don't quite understand - it doesn't seems to match the
contract in the manual.

Can anyone make any suggestions as to what I'm doing wrong?
[I'm using 3.99.0.23 [3m], built from source and running on Eee Xandros(debian)]

> (finder:common-get-file-list
  #f
  "get-folder"
  #f
  "not right"
  #f)

. framework broke the contract
  (->*
   ()
   ((or/c false/c path?)
    string?
    (or/c false/c byte-regexp?)
    string?
    (or/c
     false/c
     (is-a?/c interface:top-level-window<%>)))
   (or/c (listof path?) false/c))
on finder:common-get-file-list; expected <(or/c (listof path?)
false/c)>, given: #<void>
>
>