Index: web/typo3/sysext/core/Classes/Authentication/AbstractUserAuthentication.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/web/typo3/sysext/core/Classes/Authentication/AbstractUserAuthentication.php b/web/typo3/sysext/core/Classes/Authentication/AbstractUserAuthentication.php
--- a/web/typo3/sysext/core/Classes/Authentication/AbstractUserAuthentication.php	
+++ b/web/typo3/sysext/core/Classes/Authentication/AbstractUserAuthentication.php	(date 1658481372454)
@@ -1333,14 +1333,14 @@
         $this->user['ses_data'] = serialize($this->sessionData);
         $this->logger->debug('setAndSaveSessionData: ses_id = ' . sha1($this->id));
         //id is NULL on CLI
-        if ($this->id) {
+        if (!empty($this->id)) {
             $updatedSession = $this->getSessionBackend()->update(
                 $this->id,
                 ['ses_data' => $this->user['ses_data']]
             );
             $this->user = array_merge($this->user ?? [], $updatedSession);
         }
-        $this->user = array_merge($this->user ?? [], $updatedSession);
+        $this->user = array_merge($this->user ?? [], $updatedSession?? []);
     }
 
     /*************************