Merge branch '5.2' into 5.3

* 5.2:
  [Form] Use !isset for checks cause this doesn't falsely include 0
  [Mailer] Fix typo in README
  sync ./phpunit in all branches

Author: nicolas-grekas

README.md

@@ -36,16 +36,20 @@ set up the `BodyRenderer`:
 
 ```php
 use Symfony\Bridge\Twig\Mime\BodyRenderer;
+use Symfony\Bridge\Twig\Mime\TemplatedEmail;
 use Symfony\Component\EventDispatcher\EventDispatcher;
 use Symfony\Component\Mailer\EventListener\MessageListener;
+use Symfony\Component\Mailer\Mailer;
+use Symfony\Component\Mailer\Transport;
 use Twig\Environment as TwigEnvironment;
 
 $twig = new TwigEnvironment(...);
-$messageListener = new MessageListener(new BodyRenderer($twig));
+$messageListener = new MessageListener(null, new BodyRenderer($twig));
 
 $eventDispatcher = new EventDispatcher();
 $eventDispatcher->addSubscriber($messageListener);
 
+$transport = Transport::fromDsn('smtp://localhost', $eventDispatcher);
 $mailer = new Mailer($transport, null, $eventDispatcher);
 
 $email = (new TemplatedEmail())
@@ -56,7 +60,7 @@ $email = (new TemplatedEmail())
         'username' => 'foo',
     ])
 ;
-$mailer->mail($email);
+$mailer->send($email);
 ```
 
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