http://musicbrainz.org/edit/27770025 is such an edit, which is failing in ModBot at present. The display apparently doesn't show it, but you can see it in the raw data: http://musicbrainz.org/edit/27770025/data

I'm not sure how this was made possible but it shouldn't be possible to submit it from the RE in that state (or, relatedly, with multiple events for the same non-null country).