Exception has been thrown in "beforeScenario" hook

The error I was getting with symfony 2.3:

```
[Behat\Behat\Exception\ErrorException]                                                                                                                               
  Exception has been thrown in "beforeScenario" hook, defined in Knp\FriendlyContexts\Context\SwiftMailerContext::initContext()                                        
                                                                                                                                                                       
  Notice: Undefined variable: start in vendor/symfony/symfony/src/Symfony/Component/HttpKernel/Profiler/Profiler.php line 175
```