11.x improve resend transport response handling - fix (#54006)

* [11.x] Improve Resend transport response handling

* [11.x] Fix/Improve Resend transport response handling - adjusted throw_if condition

Author: markovic-nikola

src/Illuminate/Mail/Transport/ResendTransport.php

@@ -99,7 +99,7 @@ protected function doSend(SentMessage $message): void
                 'attachments' => $attachments,
             ]);
 
-            throw_if($result['statusCode'] != Response::HTTP_OK, Exception::class, $result['message']);
+            throw_if(isset($result['statusCode']) && $result['statusCode'] != Response::HTTP_OK, Exception::class, $result['message']);
         } catch (Exception $exception) {
             throw new TransportException(
                 sprintf('Request to Resend API failed. Reason: %s.', $exception->getMessage()),