Deleting clef does not delete courtesy clef (sometimes does not even delete selected clef)

Ubuntu Studio 14.04, GIT commit: 5373c93

1) new score, 32 measures
2) fill first six measures with notes
3) add line break after measure 4
4) drag alto clef to first measure of second system
5) select clef you just added
6) delete

Result: nothing happens except clef gets deselected

7) select and delete again

Result: clef is deleted but courtesy clef remains

8) delete line break

Result: the courtesy clef still remains and now appears to be a real clef, but the notes are displayed as for the original treble clef

Depending on how the clef change was created, sometimes the first symptom (nothing happening upon first attempt to delete clef) does not occur. For instance, if the clef is actually added to the last measure of a system but that act causes the measure to move to the next system, you can then delete the clef at the start of the next system in only one try - but the courtesy clef remains.