Clef reverts to default when Hide Clef is checked, crash on change/undo

Problem: I am trying to create a 2-line staff with a single flat sign on the top line. This is a configuration used in writing out Chant in the hymnal of the Episcopal church in the USA ("The Hymnal 1982"). If I use the "Mezzo-Soprano" clef, it produces this configuration, but I don't want the clef to show. I have unchecked the "Show Clef" and the "Show Time Signature" boxes in the "Staff/Part Properties" window, but it only works for the first measure. Once I add notes to any subsequent measure, the whole thing reverts to the G-Clef. If I fiddle with the file too much, MuseScore crashes.

This only seems to happen if the Show Clef box is unchecked. The work-around I am using leaves that box checked, but then I use the Inspector to make the Clef invisible.

Here's how I created the file:

1. Create a file with only one line in the treble clef (I used Oboe as the instrument) and set the Key to F-major (one flat).
2. Go to the Staff/Part Properties window and change the number of barlines to "2", and also uncheck Show Clef and Show Time Signature
3. Exit the Staff/Parts Properties window.
4. Set the Clef to "Mezzo-Soprano" (Middle C on the second line from the bottom)

At this point, the first measure looks right but the the flat on the next line is still down below the staff where it would be if there were five lines on the staff and the Clef were the G-Clef. If you go back to the Staff/Parts Properties window, and recheck the Show Clef box, you find that the Clef has reverted to the G-Clef.

Here are two examples, the first is a scan from the hymnal and the second is the MuseScore file.

2-line_Chant 2.mscz