add additional check to avoid selector formula right-hand side consisting of a nullary constructor getting interpreted as a discriminator formula
add additional check to avoid selector formula right-hand side consisting of a nullary constructor getting interpreted as a discriminator formula

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