[consensus] print log when participants is empty

Signed-off-by: Leo Chen <leo@harmony.one>

consensus/consensus_service.go

@@ -92,6 +92,10 @@ func (consensus *Consensus) UpdatePublicKeys(pubKeys []bls_cosi.PublicKeyWrapper
 		consensus.LeaderPubKey = &allKeys[0]
 		utils.Logger().Info().
 			Str("info", consensus.LeaderPubKey.Bytes.Hex()).Msg("My Leader")
+	} else {
+		utils.Logger().Error().
+			Msg("[UpdatePublicKeys] Participants is empty")
+		consensus.pubKeyLock.Unlock()
 	}
 	consensus.pubKeyLock.Unlock()
 	// reset states after update public keys