Potential bug in `zapFragileUnfolding`

Currently it's defined like this:

zapFragileUnfolding :: Unfolding -> Unfolding
-- ^ Zaps any core unfolding, but /preserves/ evaluated-ness,
-- i.e. an unfolding of OtherCon
zapFragileUnfolding unf
 | hasCoreUnfolding unf = noUnfolding
 | otherwise            = unf

But that's a bit odd. Clearly if the unfolding is something like Just 1 :: Maybe Int that's evaluated and a core unfolding. But we will lose the evaluatedness of this unfolding in the current implementation!

Rather it should probably be:

zapFragileUnfolding :: Unfolding -> Unfolding
-- ^ Zaps any core unfolding, but /preserves/ evaluated-ness,
-- i.e. an unfolding of OtherCon
zapFragileUnfolding unf
 | isEvaldUnfolding unf = evaldUnfolding
 | otherwise            = noUnfolding