because `dashboard_groups` does not exists:

````yml
sonata_admin:
    dashboard:
        groups:
            foo: ...
````

Is this in XML:
````xml
<sonata-admin:config>
    <dashboard>
        <group id="foo" ... />
    </dashboard>
</sonata-admin:config>
````

So I removed this one (it results in an error) and replaced it with a `fixXmlConfig('group')` on the `dashboard` node