bug symfony#36518 [Security] Fix missing nullable in CsrfTokenBadge (…

…sstok)

This PR was merged into the 5.1-dev branch.

Discussion
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[Security] Fix missing nullable in CsrfTokenBadge

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       |
| License       | MIT
| Doc PR        |

Related to symfony#33558 I noticed a minor 🤏  bug with the method return-type.

Commits
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5cb633c Update CsrfTokenBadge.php

src/Symfony/Component/Security/Http/Authenticator/Passport/Badge/CsrfTokenBadge.php

@@ -45,7 +45,7 @@ public function getCsrfTokenId(): string
         return $this->csrfTokenId;
     }
 
-    public function getCsrfToken(): string
+    public function getCsrfToken(): ?string
     {
         return $this->csrfToken;
     }