Missing clef change when no rhythms in the music

[craigsapp]

There should be a treble clef change in this example:

If there is one explicit rhythm before the clef change, then the clef change is shown:

Test data:

**kern
*clefF4
C
D
E
F
G
A
B
*clefG2
c
d
e
f
g
a
b
cc
=
*-

Open in VHV

The problem is that the rhythmless notes are probably treated as having zero duration, and the treble clef is ignored somehow because if it. The clef change is never added to the MEI conversion:

Click to view MEI conversion of first example

```xml