Returning None is the correct Python way if nothing is selected (canceled). Returning nothing is different than returning an empty string.

result = poser.DialogSimple.AskMenu(...)
if result:
   do_something()
else:
    forget_it()

In Python None is assumed as False.

for item in emptylist or listwithcontent:
    print(item_from_listwithcontent)

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