Instance Slider don't work in Glyphs 2.6 / MacOs Sierra 10.12.4 (16E195)

[etunni]

This is the message at Macro window
Start
Traceback (most recent call last):
File "Instance Slider.py", line 23, in
while len(av) < 6:
NameError: global name 'av' is not defined
End