Steps to reproduce

1. Use eZ Platform in `dev` mode with WebToolbar enabled
2. Go to AdminUI
3. Click on eZ logo in the toolbar

Result
The following exception is thrown:

An exception has been thrown during the rendering of a template ("Catchable Fatal Error: Object of class EzSystems\EzPlatformSiteFactory\Values\Site\SiteQuery could not be converted to string").

Expected results
The toolbar loads normally.