Making a list argument reliably optional

[Robin Bannister]

Hallo all

I'm having unexpected problems with a music function.
It takes several arguments, the first of which expects a list,
and should be optional.

Today it tripped up when run with a late 2.19 version and I narrowed 
this down to 2.19.39. It seemed to have trouble with the second 
parameter so I set up test cases where this varied, expecting a mixture 
of good and bad.  But instead I got a confusing mixture of bad and bad, 
including a 2.18.2 failure.  See listargtest.ly.


The music function chordRepeats has a similar first argument for 
event-types but that hasn't helped me see what I am doing wrong.
I suppose it's me or my computer that's wonky, so I would be glad of
a fresh eye or a second opinion.


Cheers,
Robin

listargtest.ly
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