flu on "printDownloadAlbumZipURL ?"

Hi,
I'm trying to use the function printDownloadAlbumZipURL from the Downloadlist plugin which I've enabled, so I wrote this in my image.php theme :
<?php printDownloadAlbumZipURL('Download album','','false'); ?>

but all I get is this message :
Fatal error: Call to a member function isDynamic() on a non-object in /home/xxx/public_html/zp-core/zp-extensions/downloadList.php on line 556

Do you know how to make it work ?

I use Zenphoto 1.4.6
theme : Zpbase
PHP : 5.3.28
MySQL : 5.1.67

Thanks.