fix empty map check

Author: sukunrt

gossipsub.go

@@ -1388,9 +1388,10 @@ func (gs *GossipSubRouter) rpcs(msg *Message) iter.Seq2[peer.ID, *RPC] {
 			}
 
 			// gossipsub peers
-			gmap, ok := gs.mesh[topic]
-			if !ok || len(gmap) == 0 {
-				// we are not in the mesh for topic, use fanout peers
+			gmap := gs.mesh[topic]
+			if len(gmap) == 0 {
+				// we are not in the mesh for topic or our mesh is empty
+				// use fanout peers for publishing
 				gmap = gs.getFanoutPeersForPublishing(topic)
 			}
 
@@ -1489,11 +1490,7 @@ func (gs *GossipSubRouter) Join(topic string) {
 			return !direct && !doBackOff && gs.score.Score(p) >= 0
 		})
 		gmap = peerListToMap(peers)
-		// It is possible that we do not have any peers subscribed to this topic yet so continue fanout
-		// to ensure that messages we publish in the intermin are not lost
-		if len(gmap) > 0 {
-			gs.mesh[topic] = gmap
-		}
+		gs.mesh[topic] = gmap
 	}
 
 	for p := range gmap {