diff --git a/src/etc/inc/legacy_bindings.inc b/src/etc/inc/legacy_bindings.inc
index 7f93e27b6..5311ca64b 100644
--- a/src/etc/inc/legacy_bindings.inc
+++ b/src/etc/inc/legacy_bindings.inc
@@ -75,6 +75,8 @@ function legacy_html_escape_form_data(&$settings)
         foreach ($settings as $dataKey => &$dataValue) {
             if (is_array($dataValue)) {
                 legacy_html_escape_form_data($dataValue);
+            } elseif ($dataValue === null) {
+                $settings[$dataKey] = '';
             } else {
                 $settings[$dataKey] = htmlspecialchars($dataValue, ENT_QUOTES | ENT_HTML401);
             }
diff --git a/src/www/system_groupmanager.php b/src/www/system_groupmanager.php
index 611746628..ba3f3825a 100644
--- a/src/www/system_groupmanager.php
+++ b/src/www/system_groupmanager.php
@@ -34,7 +34,7 @@ require_once("guiconfig.inc");
 $a_group = &config_read_array('system', 'group');
 
 if ($_SERVER['REQUEST_METHOD'] === 'GET') {
-    if (isset($a_group[$_GET['groupid']])) {
+    if (isset($_GET['groupid']) && isset($a_group[$_GET['groupid']])) {
         $id = $_GET['groupid'];
     }
     if (isset($_GET['act']) && ($_GET['act'] == 'edit' || $_GET['act'] == 'new')) {
@@ -436,7 +436,7 @@ $( document ).ready(function() {
                        class="btn btn-default btn-xs" data-toggle="tooltip" title="<?= html_safe(gettext('Edit')) ?>">
                         <span class="fa fa-pencil fa-fw"></span>
                     </a>
-<?php if ($group['scope'] != 'system'): ?>
+<?php if (isset($group['scope']) && $group['scope'] != 'system'): ?>
                     <button type="button" class="btn btn-default btn-xs act-del-group"
                         data-groupname="<?=$group['name'];?>"
                         data-groupid="<?=$i?>" title="<?= html_safe(gettext('Delete')) ?>" data-toggle="tooltip">
diff --git a/src/www/system_usermanager_passwordmg.php b/src/www/system_usermanager_passwordmg.php
index 39461fec3..966595c5f 100644
--- a/src/www/system_usermanager_passwordmg.php
+++ b/src/www/system_usermanager_passwordmg.php
@@ -64,7 +64,7 @@ if ($_SERVER['REQUEST_METHOD'] === 'GET') {
         $savemsg = gettext('Your password does not match the selected security policies. Please provide a new one.');
     }
 
-    $pconfig['language'] = $userFound ? $config['system']['user'][$userindex[$username]]['language'] : null;
+    $pconfig['language'] = $userFound ? $config['system']['user'][$userindex[$username]]['language'] ?? '' : null;
 } elseif ($_SERVER['REQUEST_METHOD'] === 'POST') {
     $input_errors = array();
     $pconfig = $_POST;