Some bbdb and Gnus window configuration help needed

[Tassilo Horn]

Hi,

I try to add a new window configuration for the article buffer. It
should be like the default one, if the current article's poster is not
in my bbdb. But if there's one it should show the bbdb buffer right of
the article buffer.

This is what I've tested so far, but doesn't work:

(gnus-add-configuration
 '(article
   (cond
     (gnus-use-trees
      '(vertical 1.0
        (summary 0.25 point)
        (tree 0.25)
        (article 1.0)))
     (t
      '(vertical 1.0
        (summary 0.25 point)
        (if (bbdb/gnus-show-sender); poster in bbdb?
            '(horizontal
              (article 90) ; 90 columns for article buffer
              (bbdb 1.0))  ; rest for bbdb
            (article 1.0))))))) ; no entry -> all for article

The problem is that `bbdb/gnus-show-sender' doesn't provide a correct
return value to `if'. The error message is:

,----
| if: Wrong type argument: number-or-marker-p, nil
`----

I've read through the bbdb info page but didn't find another function
which tests if the current article's poster is in my bbdb file returning
t or nil.

Is there one? 

If not, can anybody help my writing one? 

Much thanks in advance,
Tassilo
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