"[list 1 2 3( -> [pack 10 20 30 40]" will overwrite the first 3 elements ot [pack] and then trigger the output of the packed list.
but sending an empty list, e.g. "[list( -> [pack 10 20 30 49]", will be silently ignored.
the expected bahaviour is that no elements of [pack] are replaced and that the packed list is sent to the outlet.
the attached patch fixes this, by only calling obj_list() is the list is non-empty (obj_list() will immediately return if it gets an empty list) and instead call pack_bang() in this case.