Work around the panic thrown by IntervalDigestFromBytes

[Wondertan]

IntervalDigestFromBytes is meant to deserialize bytes commonly received from the wire that does not guarantee to compel with the panic check, allowing a non-valid network message to kill an application that uses the lib. We can either:

1. Throw an error instead
2. Force lib user to do an additional check before or recover from panic :)

But obviously, the first one is more preferable.

[Wondertan]

@liamsi, If this seems like a valid issue, I would like to resolve it.

I would also suggest keeping the same pattern(data validation in deserializer returning errors) over all the repos to reduce DOS attack vectors.

[liamsi]

That's to prevent creating any invalid IntervalDigest object. It's not meant to be used for random messages received from the network. As far as I know it is currently only used in tests. IMO, we could consider deleting it. It has low priority though.

[Wondertan]

It is used here. As an application user, I meant LL core.

That's to prevent creating any invalid IntervalDigest object

I see, however imagine a faulty Node sending a valid protobuf message, but with an empty digest. In such a case the node will panic while returning an error will keep it alive.

[liamsi]

You are right! We should fix this then. I'm still wondering if we should remove the interval digest type completely 🤔 OK. let's keep it for now and change it to return an error. Afterwards we should tag another release here and update the dependency in LL core.