[SecurityBundle] fix wrong view behavior in WebDebugToolbar when username of token is empty

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT
| Doc PR        | 

Sometimes the username of the authentication token is empty but the user is authenticated.
In that case the WebDebugToolbar displayed the user is not authenticated - what was wrong.