fix some regressions introduced in #413 (#416)

Author: dunglas

src/DomCrawler/Field/FormFieldTrait.php

@@ -54,7 +54,7 @@ public function getValue()
 
     public function isDisabled(): bool
     {
-        return null === $this->element->getAttribute('disabled') ? false : true;
+        return null !== $this->element->getAttribute('disabled');
     }
 
     private function setTextValue($value): void

tests/DummyKernel.php

@@ -16,26 +16,20 @@
 use Symfony\Component\Config\Loader\LoaderInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpKernel\Bundle\BundleInterface;
 use Symfony\Component\HttpKernel\KernelInterface;
 
 /**
  * @author Kévin Dunglas <[email protected]>
  */
 class DummyKernel implements KernelInterface
 {
-    public function serialize(): void
+    public function handle(Request $request, $type = self::MASTER_REQUEST, $catch = true): Response
     {
     }
 
-    public function unserialize($serialized): void
-    {
-    }
-
-    public function handle(Request $request, $type = self::MASTER_REQUEST, $catch = true)
-    {
-    }
-
-    public function registerBundles()
+    public function registerBundles(): iterable
     {
     }
 
@@ -55,7 +49,7 @@ public function getBundles(): array
     {
     }
 
-    public function getBundle($name, $first = true): \Symfony\Component\HttpKernel\Bundle\BundleInterface
+    public function getBundle($name, $first = true): BundleInterface
     {
     }