[HttpFoundation] Fixed #3053

src/Symfony/Component/HttpFoundation/Request.php

@@ -931,7 +931,7 @@ class Request
     {
         $preferredLanguages = $this->getLanguages();
 
-        if (null === $locales) {
+        if (empty($locales)) {
             return isset($preferredLanguages[0]) ? $preferredLanguages[0] : null;
         }
 

tests/Symfony/Tests/Component/HttpFoundation/RequestTest.php

@@ -719,6 +719,7 @@ class RequestTest extends \PHPUnit_Framework_TestCase
     {
         $request = new Request();
         $this->assertEquals('', $request->getPreferredLanguage());
+        $this->assertEquals('', $request->getPreferredLanguage(array()));
         $this->assertEquals('fr', $request->getPreferredLanguage(array('fr')));
         $this->assertEquals('fr', $request->getPreferredLanguage(array('fr', 'en')));
         $this->assertEquals('en', $request->getPreferredLanguage(array('en', 'fr')));