merged branch GromNaN/null-controller (PR #775)

This PR was merged into the master branch.

Discussion
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[Security] Make fake routes dumpable by setting NULL as controller

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #774
| License       | MIT

By setting `NULL` as controller, the route will end in 404 error if it's not bypassed by a security listener.

Commits
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5e2c4b62 Use null controller as fake route to be dumpable

src/Silex/Provider/SecurityServiceProvider.php

@@ -541,7 +541,7 @@ class SecurityServiceProvider implements ServiceProviderInterface
         foreach ($this->fakeRoutes as $route) {
             list($method, $pattern, $name) = $route;
 
-            $app->$method($pattern, function() {})->bind($name);
+            $app->$method($pattern, null)->bind($name);
         }
     }