Go into Advanced editor
Click credits for a track where the artist is wrong/non-existent
PROBLEM 1 - initially the link beside "Preview" goes to http://musicbrainz.org/artist/
Search for an artist that exists - now this link seems correct
Now type some garbage into the artist box say "fgsgdsd" or some artist that doesn't exist
PROBLEM 2 - Preview text updates to "fgsgdsd" but link still goes to the valid artist you chose earlier.

In such a cases the Preview link should either do nothing or it should not be a link.