jackdaw on "Fatal error with custom latest.php"

I'm using a custom php page to show my latest images. I get this fatal error at the beginning of the page where I have my h2 tag:

Fatal error: Call to a member function getNumImages() on a non-object in /srv/jackdaw/www/www.jacktummers.nl/collectie/zp-core/template-functions.php on line 1905

And this is what I have between the h2 tags:

<h2><?php
$zoekopdracht = getSearchWords();
if ($zoekopdracht) {
if (($total = getNumImages() + getNumAlbums()) > 0) {
if (isset($_REQUEST['date'])) {
$searchwords = getSearchDate();
} else {
$searchwords = getSearchWords();
}
echo 'Gevonden op ' . $searchwords . ' (' . $total . ')';
}
$c = 0;

} else if (isImagePage() || isAlbumPage()) {
printParentBreadcrumb('',' » ',' » '); printAlbumBreadcrumb();
} else {
echo "Nieuwste foto's";
}
?>
</h2>

I guess I made a mistake somewhere, but I can't find it.