[Security] [Firewall] Bug fixed in SimplePreAuthenticationListener when createToken() not return TokenInterface object

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | no
| Fixed tickets | 
| License       | MIT
| Doc PR        | 
you are still modifying the behavior of the code when adding this return statement here.

the code ``if ($this->simpleAuthenticator instanceof AuthenticationSuccessHandlerInterface) {`` below cannot be reached anymore while it was previously