merged branch jakzal/dockblock-void-null-fix (PR #9026)

This PR was squashed before being merged into the 2.2 branch (closes #9026).

Discussion
----------

[FrameworkBundle][Security] Replaced void return type with null for consistency

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

We're using `null` everywhere else.

Commits
-------

e4100ac [FrameworkBundle][Security] Replaced void return type with null for consistency

src/Symfony/Bundle/FrameworkBundle/Templating/GlobalVariables.php

@@ -26,6 +26,9 @@ class GlobalVariables
 {
     protected $container;
 
+    /**
+     * @param ContainerInterface $container The DI container
+     */
     public function __construct(ContainerInterface $container)
     {
         $this->container = $container;
@@ -46,7 +49,7 @@ class GlobalVariables
     /**
      * Returns the current user.
      *
-     * @return mixed|void
+     * @return mixed
      *
      * @see TokenInterface::getUser()
      */

src/Symfony/Component/Security/Core/User/UserInterface.php

@@ -80,8 +80,6 @@ interface UserInterface
      *
      * This is important if, at any given point, sensitive information like
      * the plain-text password is stored on this object.
-     *
-     * @return void
      */
     public function eraseCredentials();
 }