Fix an issue where we don't have the rpc so we dont have to close it

ethereum.go

@@ -339,7 +339,9 @@ func (s *Ethereum) Stop() {
 
 	close(s.quit)
 
+	if s.RpcServer != nil {
 		s.RpcServer.Stop()
+	}
 	s.txPool.Stop()
 	s.stateManager.Stop()