fix: treat empty dnsaddr answer as no addresses

[tabcat]

Description

@multiformats/dns 1.0.15 changed query() to throw an empty-answer error (so it can fall through to other resolvers) instead of returning an empty result. As a side effect, dialing a /dnsaddr/ that resolves to no records started rejecting with DNSQueryFailedError instead of NoValidAddressesError.

This catches the empty-answer case in the dnsaddr resolver so those dials fail with NoValidAddressesError again, while genuine DNS failures still surface as DNSQueryFailedError.

Notes & open questions

Root cause is multiformats/js-dns#34 (released in @multiformats/dns 1.0.15). No new test needed: the existing connections.spec.ts "should fail to dial if resolve fails and there are no addresses to dial" test exercises this path (it was failing on 1.0.15, passes with this change).

Change checklist

• I have performed a self-review of my own code
• I have added tests that prove my fix is effective or that my feature works

[tabcat]

It's probably more helpful to throw the DNS error but this gets everything working with the same behavior as before. We can decide on what error to throw later.