See please comment in code.
file-unattach.php li ~95
function load_dependencies(){
if(is_admin() && !class_exists('FunAdmin'))
require_once(dirname(__FILE__).'/admin.php');
//[alx359] When image-store not installed, this #include produces multiple redundant calls
//to pre_get_images/db via pre_get_posts hook, and incompatibility with cleaner-gallery WP::get_children()
//elseif(!class_exists('ImStoreFront'))
//require_once(dirname(__FILE__).'/front.php');
}
Would suggest a check for !empty constant or global specific to image-store, before #include of front.php.