main.CRITICAL: TypeError: strtotime() expects parameter 1 to be string, null

main.CRITICAL: TypeError: strtotime() expects parameter 1 to be string, null given in ...security/Model/AdminSessionInfo.php:136

Author: kanhaiya5590

app/code/Magento/Security/Model/AdminSessionInfo.php

@@ -133,7 +133,11 @@ public function isSessionExpired()
         $currentTime = $this->dateTime->gmtTimestamp();
         $lastUpdatedTime = $this->getUpdatedAt();
         if (!is_numeric($lastUpdatedTime)) {
-            $lastUpdatedTime = strtotime($lastUpdatedTime);
+            if($lastUpdatedTime === null) {
+                $lastUpdatedTime = 0;
+            }else {
+                $lastUpdatedTime = strtotime($lastUpdatedTime);
+            }
         }
 
         return $lastUpdatedTime <= ($currentTime - $lifetime) ? true : false;