bending: microtone TabNoteHeaded printed if in a chord

[Federico Bruni]

Why is the TabNoteHead printed in the attached example?
It happens only when using a chord.

A related question: if this is not a bug and I'm forced to tweak the 
transparency of the TabNoteHead, how can I save the tweak in a 
variable? I think that it's not possible and I should use a function 
instead, right?

Harm, any ideas? (see comments in the attached file)

Thanks
Federico

microtone-bending.ly
Description: Text Data

bend.ily
Description: Text document