DOMAIN MAPPING and PHP 7.1

I have installed PHP 7.1 to try it out. I have set one site to use PHP 7.1 and i've left the other ones intact with PHP 7.0.14 which works as it should.
The problem i got was 500 error.

[29-Dec-2016 14:03:57 UTC] PHP Fatal error:  Uncaught Error: [] operator not supported for strings in /path/public_html/wp-content/plugins/domain-mapping/classes/Domainmap/Module/Cdsso.php:350
Stack trace:
#0 /path/public_html/wp-includes/class-wp-hook.php(298): Domainmap_Module_Cdsso->add_query_var_for_endpoint('')
#1 /path/public_html/wp-includes/class-wp-hook.php(323): WP_Hook->apply_filters(NULL, Array)
#2 /path/public_html/wp-includes/plugin.php(453): WP_Hook->do_action(Array)
#3 /path/public_html/wp-settings.php(449): do_action('init')
#4 /path/public_html/wp-config.php(148): require_once('/path/...')
#5 /path/public_html/wp-load.php(37): require_once('/path/...')
#6 /path/public_html/wp-admin/admin.php(31): require_once('/path/...')
#7 /path/public_html/wp-admin/index.php(10): require_once('/path/...')
#8 {main}
  thrown in /path/public_html/wp-content/plugins/domain-mapping/classes/Domainmap/Module/Cdsso.php on line 350

Cdsso.php ->

function add_query_var_for_endpoint($vars) {
                add_rewrite_endpoint( self::SSO_ENDPOINT, EP_ALL );
                $vars[] = self::SSO_ENDPOINT;  <--- Line 350
                $this->_flush_rewrite_rules();
                return $vars;
        }

I removed the array since self::SSO_ENDPOINT seems to be a string.
$vars = self::SSO_ENDPOINT
After I saved that the site was reachable again

Problem with: Fatal error: [] operator not supported for strings in [closed]