Hotfix: catch a few NoneType exceptions

[daisieh]

While turning containers on and off, I noted that federation's heartbeat daemon gets very unhappy if Vault is sealed and keeps throwing exceptions for NoneTypes. These fixes should help.

Before this, you can see what I mean by stopping the vault container. Federation service will start respawning the heartbeat process over and over because servers is None. If you recompose federation at this point, you'll also see more exceptions thrown during initialization.

After pulling this fix and recomposing federation, you should see that it more gracefully handles the sealed vault in both cases.

To get everything working again, start vault again and restart vault-runner. That will unseal the vault. If you wait about a minute for opa-runner and vault-runner to refresh their tokens, you can recompose federation and everything should be as it was.

[OrdiNeu]

Looks good to me ✔️ I'll note that even after recomposing vault & federation with this though, that federation won't setup properly. I don't know if that's in the scope of this ticket.