nnir setup help: wrong type argument: arrayp, nil

[pranav@PRANAV-W2K02.i-did-not-set--mail-host-address--so-tickle-me (Pranav K. Tiwari)]

I am trying to set up nnir for indexing nnml folders, and am having some
trouble. When I try to search for something, the search succeeds, but then
it fails while showing the results with the following traceback given
below.

nnir-version's value is 
"$Id: nnir.el,v 1.1.1.1 2003/04/04 20:16:09 lolando Exp $"

My nnir configuration is also included below.

Can anyone tell me what's broken?

thx,
-p

,----[ .gnus snippet ]
| (require 'nnir)
| (setq nnir-swish-e-index-file
|       (expand-file-name "d:/pranav/mail/swish-e/index.swish-e"))
| (setq nnir-swish-e-program
|       (expand-file-name "d:/swish-e/swish-e"))
| (setq nnir-swish-e-additional-switches '())
| (setq nnir-mail-backend (nth 0 gnus-secondary-select-methods)
|       nnir-search-engine 'swish-e)
`----


,----[ traceback ]
| Debugger entered--Lisp error: (wrong-type-argument arrayp nil)
|   aset(nil 0 1)
|   (mail-header-set-number novitem idx)
|   (while (not (null artlist)) (setq art (car artlist)) (or (numberp art) (nnheader-report ... "nnir-retrieve-headers doesn't grok message ids: %s" art)) (setq artitem (nnir-artlist-article nnir-artlist art)) (setq artrsv (nnir-artitem-rsv artitem)) (setq artgroup (nnir-artitem-group artitem)) (setq artno (nnir-artitem-number artitem)) (setq artfullgroup (nnir-group-full-name artgroup)) (set-buffer nntp-server-buffer) (case (setq foo ...) (nov ... ... ...) (headers ... ... ...) (t ...)) (mail-header-set-number novitem idx) (mail-header-set-from novitem (mail-header-from novitem)) (mail-header-set-subject novitem (format "[%d: %s/%d] %s" artrsv artgroup artno ...)) (push novitem novdata) (setq artlist (cdr artlist)) (setq idx (1+ idx)))
|   (let ((artlist ...) (idx 1) (art nil) (artitem nil) (artgroup nil) (artno nil) (artrsv nil) (artfullgroup nil) (novitem nil) (novdata nil) (foo nil)) (while (not ...) (setq art ...) (or ... ...) (setq artitem ...) (setq artrsv ...) (setq artgroup ...) (setq artno ...) (setq artfullgroup ...) (set-buffer nntp-server-buffer) (case ... ... ... ...) (mail-header-set-number novitem idx) (mail-header-set-from novitem ...) (mail-header-set-subject novitem ...) (push novitem novdata) (setq artlist ...) (setq idx ...)) (setq novdata (nreverse novdata)) (set-buffer nntp-server-buffer) (erase-buffer) (mapcar (quote nnheader-insert-nov) novdata) (quote nov))
|   (save-excursion (let (... ... ... ... ... ... ... ... ... ... ...) (while ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...) (setq novdata ...) (set-buffer nntp-server-buffer) (erase-buffer) (mapcar ... novdata) (quote nov)))
|   nnir-retrieve-headers((1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 ...) "((query . \"test\"))" "-ephemeral" nil)
|   gnus-retrieve-headers((1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 ...) "nnir:((query . \"test\"))" nil)
|   gnus-fetch-headers((1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 ...))
|   gnus-select-newsgroup("nnir:((query . \"test\"))" t nil)
|   gnus-summary-read-group-1("nnir:((query . \"test\"))" t t nil nil nil)
|   gnus-summary-read-group("nnir:((query . \"test\"))" t t nil nil nil nil)
|   gnus-group-read-group(t t "nnir:((query . \"test\"))" nil)
|   byte-code("\b	\x1a^[Ælj\f$*…\x0f|   gnus-group-read-ephemeral-group("nnir:((query . \"test\"))" (nnir "") t (#<buffer *Group*> . group) nil)
|   (let ((parms nil)) (if extra-parms (setq parms ...) (setq parms ...)) (gnus-group-read-ephemeral-group (concat "nnir:" ...) (quote ...) t (cons ... gnus-current-window-configuration) nil))
|   gnus-group-make-nnir-group(nil "test")
`----





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