[imp] PHP warning in message view

[Otto Stolz]

Hello,

my Imp test installation issues the following warning, every time
it displays a message:
> Warning: Invalid argument supplied for foreach()
>          in /opt/test-webmail/horde/imp/message.php on line 340

That source line is concerned with displaying the user-specified
headers for the current identity.

I have indeed specified two extra headers, in imp/message.php:
> $_prefs['mail_hdr'] = array(
>     'value' => "Message-ID\nX-Spam-Level",
>     'locked' => false,
>     'shared' => false,
>     'type' => 'textarea',
>     'desc' => _("Additional headers to display when viewing: <em>(optional, enter each header  on a new line)</em>"));

And the "Personal Information" screen shows them alright::
> Additional headers to display when viewing:
> (optional, enter each header on a new line) 
>    Message-ID
>    X-Spam-Level

But the message view does not show them, on account of that
PHP error, cf. above.

So, what should I do to get this feature working?

My environment:
- Horde 3.1.1
- Imp H3 (4.1.1)
- PEAR: I don't know; imp/test says: "Recent PEAR: Yes"
- PHP 4.4.2
- Apache/1.3.34 (Unix) mod_ssl/2.8.25 OpenSSL/0.9.7e PHP/4.4.2
- Solaris: SunOS 5.9

Thanks for any hint.

Best wishes,
    Otto Stolz