Merge branch '1.11.x' of github.com:chamilo/chamilo-lms into 1.11.x

plugin/add_facebook_login_button/plugin.php

@@ -33,6 +33,9 @@ $form->addButtonSave(get_lang('Save'), 'submit_button');
 $tab_default_add_facebook_login_button_facebook_button_url = api_get_setting(
     'add_facebook_login_button_facebook_button_url'
 );
+
+$defaults = [];
+
 if ($tab_default_add_facebook_login_button_facebook_button_url) {
     $defaults['facebook_button_url'] = $tab_default_add_facebook_login_button_facebook_button_url['add_facebook_login_button'];
 }