Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p nil)
  byte-code("..." [nlist2 x high throw iterate-loop nil] 4)
  nnmaildir--nlist-iterate((...) (nil) #[(article) "..." [nnmaildir--cur-server group article nov cl-struct-nnmaildir--art-tags num nnmaildir--update-nov nnmaildir--cache-nov 0 error "nnmaildir--art-num accessing a non-nnmaildir--art" 3 princ "	" "nnmaildir--art-msgid accessing a non-nnmaildir--art" 4 1 "	Xref: nnmaildir " ":" 2 "\n" nntp-server-buffer gname] 10])
  byte-code("..." [...] 5)
  nnmaildir-retrieve-headers((nil) "lists.computer" "" nil)
  gnus-retrieve-headers((nil) "lists.computer" nil)
  (setq foo (gnus-retrieve-headers (list artno) artfullgroup nil))
  (let ((--cl-var-- ...)) (cond (... ... ... ...) (... ... ... ...) (t ...)))
  (case (setq foo (gnus-retrieve-headers ... artfullgroup nil)) (nov (goto-char ...) (setq novitem ...) (unless novitem ... ...)) (headers (goto-char ...) (setq novitem ...) (unless novitem ... ...)) (t (error "Unknown header type %s while requesting article %s of group %s" foo artno artfullgroup)))
  (let ((gnus-override-method ...)) (case (setq foo ...) (nov ... ... ...) (headers ... ... ...) (t ...)))
  (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 artfullgroup (nnir-artitem-group artitem)) (setq artno (nnir-artitem-number artitem)) (setq artgroup (gnus-group-real-name artfullgroup)) (setq server (nnir-group-server artfullgroup)) (set-buffer nntp-server-buffer) (nnir-possibly-change-server server) (let (...) (case ... ... ... ...)) (mail-header-set-number novitem art) (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)))
  (let ((artlist ...) (art nil) (artitem nil) (artgroup nil) (artno nil) (artrsv nil) (artfullgroup nil) (novitem nil) (novdata nil) (foo nil) server) (while (not ...) (setq art ...) (or ... ...) (setq artitem ...) (setq artrsv ...) (setq artfullgroup ...) (setq artno ...) (setq artgroup ...) (setq server ...) (set-buffer nntp-server-buffer) (nnir-possibly-change-server server) (let ... ...) (mail-header-set-number novitem art) (mail-header-set-from novitem ...) (mail-header-set-subject novitem ...) (push novitem novdata) (setq artlist ...)) (setq novdata (nreverse novdata)) (set-buffer nntp-server-buffer) (erase-buffer) (mapcar (quote nnheader-insert-nov) novdata) (quote nov))
  (save-excursion (let (... ... ... ... ... ... ... ... ... ... server) (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) "((query . \"steib reiner\") (unique-id . \"x8tfxvcnffh.fsf\"))" "-ephemeral" nil)
  gnus-retrieve-headers((1 2 3 4 5 6 7 8) "nnir:((query . \"steib reiner\") (unique-id . \"x8tfxvcnffh.fsf\"))" nil)
  byte-code("..." [...] 6)
  gnus-cache-retrieve-headers((1 2 3 4 5 6 7 8) "nnir:((query . \"steib reiner\") (unique-id . \"x8tfxvcnffh.fsf\"))" nil)
  gnus-retrieve-headers((1 2 3 4 5 6 7 8) "nnir:((query . \"steib reiner\") (unique-id . \"x8tfxvcnffh.fsf\"))" nil)
  gnus-fetch-headers((1 2 3 4 5 6 7 8))
  gnus-select-newsgroup("nnir:((query . \"steib reiner\") (unique-id . \"x8tfxvcnffh.fsf\"))" t nil)
  gnus-summary-read-group-1("nnir:((query . \"steib reiner\") (unique-id . \"x8tfxvcnffh.fsf\"))" t t nil nil nil)
  gnus-summary-read-group("nnir:((query . \"steib reiner\") (unique-id . \"x8tfxvcnffh.fsf\"))" t t nil nil nil nil)
  byte-code("..." [] 8)
  gnus-group-read-group(t t "nnir:((query . \"steib reiner\") (unique-id . \"x8tfxvcnffh.fsf\"))" nil)
  byte-code("..." [...] 5)
  gnus-group-read-ephemeral-group("nnir:((query . \"steib reiner\") (unique-id . \"x8tfxvcnffh.fsf\"))" (nnir "") t (#<buffer *Group*> . group) nil)
  (let ((parms nil)) (if extra-parms (setq parms ...) (setq parms ...)) (add-to-list (quote parms) (cons ... ...) t) (gnus-group-read-ephemeral-group (concat "nnir:" ...) (quote ...) t (cons ... gnus-current-window-configuration) nil))
  gnus-group-make-nnir-group(nil "steib reiner")
  call-interactively(gnus-group-make-nnir-group)