Warning illegal id

Edit: hashbuddy is not in cause.

But it does this warning on some user account, not for all.

Warning: Illegal string offset 'id' in wp-content/plugins/buddypress-activity-privacy/includes/bp-activity-privacy-filters.php on line 355

the line in the file:

if( isset($retval) && is_array($retval) && !empty( $retval) ) {
            $activity_id = $retval[0]['id'];

            $activities = bp_activity_get_specific( array( 'activity_ids' => $activity_id ) );
            $activity = $activities['activities'][0];
            $remove_from_stream = bp_visibility_is_activity_invisible( $activity, $bp_loggedin_user_id, $is_super_admin, $bp_displayed_user_id );
            if ($remove_from_stream) {
                return false;
            }
         }