minor #13244 [Debug] fix test (nicolas-grekas)

This PR was merged into the 2.6 branch.

Discussion
----------

[Debug] fix test

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

My bad, I missed this one.

Commits
-------

a2435a7 [Debug] fix test

src/Symfony/Component/Debug/Tests/ErrorHandlerTest.php

@@ -169,6 +169,8 @@ class ErrorHandlerTest extends \PHPUnit_Framework_TestCase
 
     public function testHandleError()
     {
+        $this->iniSet('error_reporting', -1);
+
         try {
             $handler = ErrorHandler::register();
             $handler->throwAt(0, true);