Merge branch '4.4'

* 4.4:
  [Bridge/PhpUnit] fix looking for composer
  cs fix
  [Mailer] fixed Mailgun support when a response is not JSON as expected
  [4.3] Cleanup tests
  Cleanup tests
  [Finder] Prevent unintentional file locks in Windows
  [FrameworkBundle] Fix about command not showing .env vars
  [DomCrawler] Fix FileFormField PHPDoc
  [Mailer] Remove the default dispatcher in AbstractTransport
  Fix #33395 PHP 5.3 compatibility

Author: nicolas-grekas

Field/ChoiceFormField.php

@@ -113,7 +113,7 @@ public function untick()
     /**
      * Sets the value of the field.
      *
-     * @param string|array $value The value of the field
+     * @param string|array|bool|null $value The value of the field
      *
      * @throws \InvalidArgumentException When value type provided is not correct
      */

Field/FormField.php

@@ -101,7 +101,7 @@ public function getValue()
      */
     public function setValue(?string $value)
     {
-        $this->value = (string) $value;
+        $this->value = $value ?? '';
     }
 
     /**