minor #17346 [2.3] Workaround https://bugs.php.net/63206 (nicolas-grekas)

This PR was merged into the 2.3 branch.

Discussion
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[2.3] Workaround https://bugs.php.net/63206

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

This bug has almost no chance to be hit in this code but still, cleaning any potential issue is worth.

Commits
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c5479dd [2.3] Workaround https://bugs.php.net/63206

src/Symfony/Component/HttpFoundation/JsonResponse.php

@@ -106,7 +106,7 @@ class JsonResponse extends Response
                     // PHP 5.3 triggers annoying warnings for some
                     // types that can't be serialized as JSON (INF, resources, etc.)
                     // but doesn't provide the JsonSerializable interface.
-                    set_error_handler('var_dump', 0);
+                    set_error_handler(function () { return false; });
                     $data = @json_encode($data, $this->encodingOptions);
                 } else {
                     // PHP 5.4 and up wrap exceptions thrown by JsonSerializable