fix(targetticket): prevent exception in inconsistent target ticket

Author: btry

inc/question.class.php

@@ -1214,7 +1214,7 @@ public function deleteObsoleteItems(CommonDBTM $container, array $exclude) : boo
     * Get the field object representing the question
     * @return PluginFormcreatorFieldInterface|null
     */
-   public function getSubField(): PluginFormcreatorFieldInterface {
+   public function getSubField(): ?PluginFormcreatorFieldInterface {
       if ($this->isNewItem()) {
          return null;
       }

inc/targetticket.class.php

@@ -1226,7 +1226,10 @@ protected function setTargetAssociatedItem(array $data, PluginFormcreatorFormAns
             // find the itemtype of the associated item
             $associateQuestion = $this->fields['associate_question'];
             $question = new PluginFormcreatorQuestion();
-            $question->getFromDB($associateQuestion);
+            if (!$question->getFromDB($associateQuestion)) {
+               Toolbox::logError(sprintf("Question ID %s not found and should be used in target ticket ID %s", $associateQuestion, $this-getID()));
+               break;
+            }
             /** @var  GlpiPlugin\Formcreator\Field\DropdownField */
             $field = $question->getSubField();
             $itemtype = $field->getSubItemtype();