fix: account for the possibility of not having enough higher peers

Signed-off-by: ljedrz <[email protected]>

Author: ljedrz

node/router/src/heartbeat.rs

@@ -245,11 +245,12 @@ pub trait Heartbeat<N: Network>: Outbound<N> {
                 .candidate_peers()
                 .into_iter()
                 .partition(|peer| peer.last_height_seen.map(|h| h > own_height).unwrap_or(false));
-            let larger_half = num_deficient.div_ceil(2);
-            for peer in higher_peers.into_iter().choose_multiple(rng, larger_half) {
+            // We may not know of half of `num_deficient` candidates; account for it using `min`.
+            let num_higher_peers = num_deficient.div_ceil(2).min(higher_peers.len());
+            for peer in higher_peers.into_iter().choose_multiple(rng, num_higher_peers) {
                 self.router().connect(peer.listener_addr);
             }
-            for peer in other_peers.into_iter().choose_multiple(rng, num_deficient - larger_half) {
+            for peer in other_peers.into_iter().choose_multiple(rng, num_deficient - num_higher_peers) {
                 self.router().connect(peer.listener_addr);
             }