Solution :

Change line 161 in  / components / com_rsgallery2 / rsgallery.php to

echo "<li>{$kid->get['id']} {$kid->get['name']}";

Change line 304  in administrator / components / com_rsgallery2 / includes / gallery.class.php  to

 " WHERE gallery_id='{$this->get['id']}'".

And it works again
Gr