minor symfony#24495 Remove unnecessary condition; (243083df)

This PR was merged into the 4.0-dev branch.

Discussion
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Remove unnecessary condition;

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | ---
| License       | MIT
| Doc PR        | ---

Commits
-------

f09f0ae Remove unnecessary condition;

Author: fabpot

src/Symfony/Component/HttpKernel/HttpKernel.php

@@ -157,9 +157,7 @@ private function handleRaw(Request $request, int $type = self::MASTER_REQUEST)
 
             if ($event->hasResponse()) {
                 $response = $event->getResponse();
-            }
-
-            if (!$response instanceof Response) {
+            } else {
                 $msg = sprintf('The controller must return a response (%s given).', $this->varToString($response));
 
                 // the user may have forgotten to return something