Default style file not clearing during session

Steps to reproduce:
1) Create a style file that varies from the default in any way. I set the music font to Bravura.
2) in the Preferences, Score tab, set the default style file to this Bravura style file
3) create a new score - voilà, it uses Bravura.
4) in the Preferences, Score tab, clear the default style file by clearing the text field. Click OK.
5) create a new score - uh oh, it uses Bravura when it should have switched back to Emmentaler.
6) close and reopen MuseScore and everything is back to a clean default.