Sent message still in drafts (lisp error: "Selecting deleted buffer")

[Felix Natter]

hi,

I am using: GNU Emacs 23.4.1 (i486-pc-linux-gnu, GTK+ Version 2.24.10)
 of 2012-09-09 on murphy, modified by Debian with Gnus v5.13.

I am often (but not always) running into the problem that although a
message has been sent (and ends up in the "sent-mail" folder), it is
still in 'drafts'. When that happens, the last message in *Messages* is:

nnml-save-mail: Selecting deleted buffer

And if I do '(setq debug-on-error t)' beforehand (but not before
starting Gnus) then I get:

Debugger entered--Lisp error: (error "Selecting deleted buffer")
  nnml-add-nov("expired" 12197 [nil "Rheinblick-Cache" "Felix Natter 
<fnatter@gmx.net>" "Sun, 10 Feb 2013 18:19:25 +0100" 
"<87pq08hyse.fsf@totally-fudged-out-message-id>" nil 0 0 "bitburger.home.felix 
expired:12197" ((To . "ulrike.natter@gmx.de"))])
  nnml-save-mail((("expired" . 12197)) "")
  nnml-request-accept-article("expired" "" nil)
  gnus-request-accept-article("nnml:expired" nil nil t)
  nnmail-expiry-target-group("nnml:expired" "drafts")
  nnmh-request-expire-articles((104) "drafts" nil t)
  apply(nnmh-request-expire-articles ((104) "drafts" nil t))
  nnoo-parent-function(nndraft nnmh-request-expire-articles ((104) "drafts" nil 
t))
  nndraft-request-expire-articles((104) "drafts" nil t)
  message-disassociate-draft()
  message-send(nil)
  message-send-and-exit(nil)
  call-interactively(message-send-and-exit nil nil)

My mails are in ~/Mail, but my drafts are in ~/News/drafts/drafts, if
that makes a difference.
I also use this:
(setq nnmail-expiry-target "nnml:expired")

Is this fixed in the Gnus contained in Emacs24?

Thanks and Best Regards!
-- 
Felix Natter