[Plugin: Simple Fields] Get an error on certain pages

Hi.
I get the following error on som pages. For instance an attachment page I get this error:

Warning: Invalid argument supplied for foreach() in /home/u11svxp/www/wordpress/wp-content/plugins/simple-fields/functions_post.php on line 748

I have this settup:

$boxes = function_exists('simple_fields_get_post_group_values') ? simple_fields_get_post_group_values(get_the_ID(), 1) : 0;

Is there a way of preventing this from happening?

Thanks
Vayu

http://wordpress.org/extend/plugins/simple-fields/