Added 404 not found exception.

src/Packagist/WebBundle/Controller/WebController.php

@@ -124,6 +124,10 @@ class WebController extends Controller
             ->getRepository('PackagistWebBundle:Package')
             ->findOneById($id);
 
+        if(empty($package))  {
+            throw new NotFoundHttpException();
+        }
+
         return array('package' => $package);
     }