Incorrect segment type for fermata

From https://musescore.org/en/node/294038.

This is a critical issue because it can result in corruption or a crash. To achieve a crash, do the following, starting with a blank score:
1. Add two notes in the first measure.
2. Move the second note to voice 2.
3. Add a fermata to the second note.
4. Delete the second note.
5. Delete all voice 2 rests in the first measure.
6. Add a clef change to the second measure.
7. Save and close. MuseScore will crash if you try to reopen the file.