bug#11594: message-send-and-exit now fails

[Jim Meyering]

I built emacs from the latest on the trunk and found
that I can no longer send mail in the usual manner (using gnus).

It worked fine with a snapshot from 2012-05-24.09h10 UTC.
Here's how it fails, now:

Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p nil)
  auth-source-search(:host "localhost" :port "smtp" :user nil :max 1 :require 
nil :create nil)
  smtpmail-try-auth-methods(#<process smtpmail> (dsn 8bitmime 
enhancedstatuscodes etrn size) "localhost" "smtp" nil)
  byte-code("...elided..." [host process-buffer buffer-undo-list 
coding-system-for-write coding-system-for-read port get-buffer-create format 
"*trace of SMTP session to %s*" t erase-buffer binary open-network-stream 
"smtpmail" :type :return-list :capability-command "EHLO %s.\n" smtpmail-fqdn 
:end-of-command "^[0-9]+ .*.\n" :success "^2.*\n" :always-query-capabilities 
:starttls-function #[(capabilities) "\301\302\"\205.\303\207" [capabilities 
string-match "[ -]STARTTLS" "STARTTLS.\n"] 3] :client-certificate 
:use-starttls-if-possible throw done plist-get :error "Unable to contact 
server" set-process-filter smtpmail-process-filter :greeting 
smtpmail-response-code "No greeting: %s" 400 "Connection not allowed: %s" 
set-buffer-process-coding-system raw-text-unix make-local-variable 
smtpmail-read-point :capabilities smtpmail-command-or-throw "HELO %s" delete "" 
split-string ...] 24)
  smtpmail-via-smtp(("11557@debbugs.gnu.org" "monnier@iro.umontreal.ca" 
"rgm@gnu.org") #<buffer  smtpmail temp>)
  smtpmail-send-it()
  message-smtpmail-send-it()
  #[nil " \207" [message-send-mail-function] 1]()
  gnus-agent-send-mail()
  message-send-mail(nil)
  message-send-via-mail(nil)
  message-send(nil)
  message-send-and-exit(nil)
  call-interactively(message-send-and-exit nil nil)