From 2f849ade8204a4b417202d90c66e2f5bef4e965d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Felf=C3=B6ldi=20Zsolt?= <zsfelfoldi@gmail.com>
Date: Sat, 10 Feb 2018 13:33:52 +0100
Subject: [PATCH] les: fix server panic when discovery disabled (#16055)

---
 les/server.go | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/les/server.go b/les/server.go
index 85ebbf898..65b8c357d 100644
--- a/les/server.go
+++ b/les/server.go
@@ -111,15 +111,17 @@ func (s *LesServer) Protocols() []p2p.Protocol {
 // Start starts the LES server
 func (s *LesServer) Start(srvr *p2p.Server) {
 	s.protocolManager.Start(s.config.LightPeers)
-	for _, topic := range s.lesTopics {
-		topic := topic
-		go func() {
-			logger := log.New("topic", topic)
-			logger.Info("Starting topic registration")
-			defer logger.Info("Terminated topic registration")
+	if srvr.DiscV5 != nil {
+		for _, topic := range s.lesTopics {
+			topic := topic
+			go func() {
+				logger := log.New("topic", topic)
+				logger.Info("Starting topic registration")
+				defer logger.Info("Terminated topic registration")
 
-			srvr.DiscV5.RegisterTopic(topic, s.quitSync)
-		}()
+				srvr.DiscV5.RegisterTopic(topic, s.quitSync)
+			}()
+		}
 	}
 	s.privateKey = srvr.PrivateKey
 	s.protocolManager.blockLoop()