minor #1600 Fix tests on PHP 7.2 (fabpot)

This PR was merged into the 2.2.x-dev branch.

Discussion
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Fix tests on PHP 7.2

Commits
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26bec42f fixed tests on PHP 7.2

tests/Silex/Tests/Provider/SessionServiceProviderTest.php

@@ -27,11 +27,6 @@ class SessionServiceProviderTest extends WebTestCase
 {
     public function testRegister()
     {
-        /*
-         * Smoke test
-         */
-        $defaultStorage = $this->app['session.storage.native'];
-
         $client = $this->createClient();
 
         $client->request('get', '/login');