cli/sync: filter seeds without an address

If a seed for syncing does not have an address, the local node will not be able
to connect to it.

These can be filtered out so that no connection attempts are made for these nodes.

crates/radicle-cli/src/commands/sync.rs

@@ -281,7 +281,10 @@ pub fn fetch(
             let candidates = connected
                 .into_iter()
                 .map(|seed| seed.nid)
-                .chain(disconnected.into_iter().map(|seed| seed.nid))
+                .chain(disconnected.into_iter().filter_map(|seed| {
+                    // Only consider seeds that have at least one known address.
+                    (!seed.addrs.is_empty()).then_some(seed.nid)
+                }))
                 .map(sync::fetch::Candidate::new);
             sync::FetcherConfig::public(settings.seeds.clone(), settings.replicas, *local)
                 .with_candidates(candidates)