[FrameworkBundle] Fixed OutOfBoundException when session handler_id is null

[FrameworkBundle] Fixed OutOfBoundException when session handler_id is null

When a null is provided for framework.session.handler_id the FrameworkExtension attempts to set the session storage to null for the 'session.storage.php_bridge' by altering the second argument. According to the session.xml service definition, there is no second argument, and it is in fact the first (read, 0 index) argument that should be changed.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #8228
| License       | MIT
| Doc PR        | N/A