new "markup" tag effect?

"Louis B. Moore" <[email protected]> Tue, 30 May 2006 21:20:46 -0600 (MDT)

Newsgroups	gmane.emacs.wiki.general
Message-ID	<[email protected]>

Hi all,

in my plan .header the following snippet:

   <head><title><lisp>
   (concat (muse-publishing-directive "title")
           (let ((author (muse-publishing-directive "author")))
             (if (not (string= author (user-full-name)))
                 (concat " (by " author ")"))))</lisp></title>


is now generating:

<hnil>2006.05.30</hnil>


on debian with  planner-el 3.40.arch.50-1 and muse-el 3.02.90.arch.144-1

is this an effect of the new <markup> tag? and how can I get back to 
generating:

<title>2006.05.30</title>


any assistance is appreciated,

Louis