This happens on rare occasions where a review discussion is started but not completed, and a dummy entry remains in the database. We’ve fixed a lot of these instances, but it seems at least one still persists. If you can reliably reproduce it, that would help us track down the cause.
That looks like an issue with the XML files loading. I’d recommend flushing the cache. If that doesn’t work, there may be more system issues with your install. You might check the error logs to see if you’re running into file permissions errors or otherwise see failed XML file loading issues.