fix(formanswer): PHP 8.1 compatbility, error message if invalid JSON detected

Author: btry

inc/targetproblem.class.php

@@ -186,7 +186,7 @@ public function save(PluginFormcreatorFormAnswer $formanswer): ?CommonDBTM {
       ];
       foreach ($problemFields as $problemFields) {
          $data[$problemFields] = $this->prepareTemplate(
-            $this->fields[$problemFields],
+            $this->fields[$problemFields] ?? '',
             $formanswer,
             $problemFields == 'content' // only content supports rich text
          );

inc/targetticket.class.php

@@ -825,7 +825,7 @@ public function save(PluginFormcreatorFormAnswer $formanswer): ?CommonDBTM {
       $data['date'] = $_SESSION['glpi_currenttime'];
 
       $data['content'] = $this->prepareTemplate(
-         $this->fields['content'],
+         $this->fields['content'] ?? '',
          $formanswer,
          $richText
       );

js/scripts.js

@@ -1392,7 +1392,14 @@ var plugin_formcreator = new function() {
             window.location = data.redirect;
          }
       }).fail(function (xhr, data) {
-         if (xhr.responseText == '' || typeof(xhr.responseJSON.message) == 'undefined') {
+         if (xhr.responseText == '') {
+            displayAjaxMessageAfterRedirect();
+            return;
+         }
+         if (typeof(xhr.responseJSON) == 'undefined') {
+            alert(i18n.textdomain('formcreator').__('An internal error occurred. Please report it to administrator.', 'formcreator'));
+         }
+         if (typeof(xhr.responseJSON.message) == 'undefined') {
             displayAjaxMessageAfterRedirect();
             return;
          }