When adding or editing a release, if you have not yet done a lookup for a track artist, but apply a Guess Case, artist name will be guess cased too.

This lead to wrong artist credit, and unneeded extra steps in "Missing entities" tab.

Steps to reproduce:
1. Go to http://musicbrainz.org/release/cb49c862-43b3-40c5-8361-dae32914518c/edit
2. Go to Tracklist tab, advanced mode and selected English Guess Case mode
3. Click on a track artist field, then click elsewhere. Background of field should now be white or red rather than green: it means no artist is selected
4. Now click on Guess case (either release-wide or track-wide): artist name is changed from "Ismael ledesma" to "Ismael Ledesma"