list_to_set_comprehension: don't crash in case distinctions on datatypes with even number of constructors
list_to_set_comprehension: don't crash in case distinctions on datatypes with even number of constructors

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle