Blank page editing Group

Trying to edit a Group gives the error

Catchable fatal error: Object of class stdClass could not be converted to string in /var/www/public_html/web/app/plugins/press-permit-core/admin/permissions-ui_pp.php on line 515

We are using HHVM and this seems to be a duplicate of the problem described in https://www.ads-software.com/support/topic/edit-user-page-blank. Applying the code change suggested in that thread

$roles = ppc_get_roles( $agent_type, $agent_id, array('post_types' => $post_types, 'taxonomies' => $taxonomies ) );

solves the problem. The thread (which is a year old) says the code fix would be applied to the next release. I guess it never made it.

https://www.ads-software.com/plugins/press-permit-core/