No longer force unwrap footer result

[aidantwoods]

Avoid force unwrapping here. I ended up using UnwrappedResults() erroneously to match the existing signature ([]byte, error) over Results() which would more safely return (*[]byte, error). The existing signature is the way it is because []byte can have a nil state, which isn't expressible at a generic level.

Add some special casing to transform the Option[[]byte] into []byte by mapping the None case to nil == []byte{}.