Problem with barre music function

[Nick Payne]

I have a music function I use for barring indications in guitar scores, and
for a reason that I haven't been able to work out, if the TextSpanner used
for the barring indication wraps from the staff where it begins to the
following staff, and also terminates at the first note of that staff, then
nothing gets drawn above that first note. If it wraps to the following staff
and terminates at any note other than the first, then it works correctly.

Test code and output attached. The second barring indication should end on
the first note of bar 16, but nothing displays.

Nick

test1.ly
Description: Text Data

test1.png
Description: PNG image