Update setting 'hide_user_field_from_list' fix #1924

Before:
$_configuration['hide_user_field_from_list'] = ['username'];

Now:
$_configuration['hide_user_field_from_list'] = ['fields' => ['username']];

main/install/configuration.dist.php

@@ -188,7 +188,7 @@ $_configuration['system_stable'] = NEW_VERSION_STABLE;
 // The default template that will be use in the system.
 //$_configuration['default_template'] = 'default'; // (main/template/default)
 // Hide fields in the main/user/user.php page
-//$_configuration['hide_user_field_from_list'] = array('username');
+//$_configuration['hide_user_field_from_list'] = ['fields' => ['username']];
 // Aspell Settings
 //$_configuration['aspell_bin'] = '/usr/bin/hunspell';
 //$_configuration['aspell_opts'] = '-a -d en_GB -H -i utf-8';

main/user/user.php

@@ -512,6 +512,7 @@ $table->set_header($header_nr++, get_lang('GroupSingle'), false);
 $hideFields = api_get_configuration_value('hide_user_field_from_list');
 
 if (!empty($hideFields)) {
+    $hideFields = $hideFields['fields'];
     foreach ($hideFields as $fieldToHide) {
         if (isset($indexList[$fieldToHide])) {
             $table->setHideColumn($indexList[$fieldToHide]);