diff --git a/Classes/Module/DmailController.php b/Classes/Module/DmailController.php
index a634b7aa1..311f3c0e9 100644
--- a/Classes/Module/DmailController.php
+++ b/Classes/Module/DmailController.php
@@ -1219,7 +1219,7 @@ protected function sendMail($row)
         } elseif ($this->cmd == DmailCmdEnum::SendMailTest->value) {
             // step 4, sending test personalized test emails
             // setting Testmail flag
-            $htmlmail->setTestmail((bool)$this->params['testmail']);
+            $htmlmail->setTestmail((bool)($this->params['testmail'] ?? false));
 
             if ($this->tt_address_uid) {
                 // personalized to tt_address
diff --git a/Classes/Plugin/DirectMail.php b/Classes/Plugin/DirectMail.php
index 8a2595903..c3d9c6d3f 100644
--- a/Classes/Plugin/DirectMail.php
+++ b/Classes/Plugin/DirectMail.php
@@ -741,11 +741,11 @@ public function renderImages(array $imagesArray, string $fieldname): string
 
         // create the image, imagelink and image caption block
         foreach ($imagesArray as $k => $image) {
-            if (strlen(trim($image['image'])) > 0) {
+            if (array_key_exists('image', $image) && strlen(trim($image['image'])) > 0) {
                 $lines[] = $image['image'];
                 if ($image['link']) {
                     $theLink = $this->getLink($image['link']);
-                    if ($theLink) {
+                    if (array_key_exists($fieldname . '.', $this->conf) && $theLink) {
                         $lines[] = $this->getString($this->conf[$fieldname . '.']['linkPrefix']) . $theLink;
                     }
                 }
@@ -758,7 +758,7 @@ public function renderImages(array $imagesArray, string $fieldname): string
                 $imageExists = true;
             }
         }
-        if ($this->conf[$fieldname . '.']['header'] && $imageExists) {
+        if (array_key_exists($fieldname . '.', $this->conf) && $this->conf[$fieldname . '.']['header'] && $imageExists) {
             array_unshift($lines, $this->getString($this->conf[$fieldname . '.']['header']));
         }
 
@@ -825,7 +825,7 @@ public function getString(string $str): string
      */
     public function userProcess(string $mConfKey, $passVar)
     {
-        if ($this->conf[$mConfKey]) {
+        if ($this->conf[$mConfKey] ?? false) {
             $funcConf = $this->conf[$mConfKey . '.'];
             $funcConf['parentObj']=&$this;
             $passVar = $GLOBALS['TSFE']->cObj->callUserFunction(
diff --git a/Classes/SelectCategories.php b/Classes/SelectCategories.php
index c24af3f3c..b86c07659 100644
--- a/Classes/SelectCategories.php
+++ b/Classes/SelectCategories.php
@@ -39,7 +39,7 @@ public function getLocalizedCategories(array &$params): void
         $lang = $this->getLang();
 
         $site = $params['site'];
-        $languages = $site->getAllLanguages();
+        $languages = $site->getAllLanguages() ?? [];
         foreach($languages as $language) {
             if($language->getLocale()->getLanguageCode() == $lang) {
                 $sysLanguageUid = $language->getLanguageId();