merged branch Tobion/mongotest (PR symfony#4082)

Commits ------- 58b2b2d fix fatal error when mongo not available Discussion ---------- fix fatal error when mongo not available

Author: fabpot

src/Symfony/Component/HttpFoundation/Tests/Session/Storage/Handler/MongoDbSessionHandlerTest.php

@@ -44,7 +44,9 @@ protected function setUp()
 
  protected function tearDown()
  {
- self::$mongo->dropDB($this->options['database']);
+ if (null !== self::$mongo) {
+ self::$mongo->dropDB($this->options['database']);
+ }
  }
 
  public function testOpenMethodAlwaysReturnTrue()