Another "Rmail" problem I ran into

[Dr Rainer Woitok <rainer.woitok@gmail.com>]

Greetings,

because sometimes  Google sends  some reply mail  to my inbox  before it
sends the corresponding original mail, I added the following lines to my
"Rmail" configuration file:

   (defun Sort-Date ()
    "Sort incoming mail by date."
    (rmail-summary-sort-by-date nil))

   (add-hook 'rmail-get-new-mail-hook 'Sort-Date)

But this leads  to either  the summary  or the message buffer  not being
displayed, and in buffer "*Messages*" I find

   Getting mail from /home/rainer/mail/.HAM...
   Counting new messages...done (1)
   Finding sort keys...30
   Reordering messages...30
   Counting messages...done
   Computing summary lines...done
   rmail-show-message: Wrong type argument: stringp, nil

Just in case it matters: including the one new message there are 39 mes-
sages in the summary buffer,  so why does "Rmail" only process 30 messa-
ges?

When I again comment out the "add-hook" line above and restart "Rmail",
everything works again (well, except for the sorting of course).

What's going wrong here?

Sincerely,
  Rainer