Polylang / Warning: Missing argument 2

I have an issue with Maintenance plugin saying:

Warning: Missing argument 2 for PLL_Admin_Sync::add_meta_boxes() in /wp-content/plugins/polylang/admin/admin-sync.php on line 46
Warning: Missing argument 2 for PLL_Plugins_Compat::cft_copy() in /wp-content/plugins/polylang/include/plugins-compat.php on line 229

https://wordpress.org/support/topic/missing-argument-14?replies=2
http://support.ait-themes.com/support/topic/108511

https://wordpress.org/plugins/maintenance/