Merge pull request #6289 from yyforyongyu/fix-fee-service-panic

itest: check feeService against nil upon shutdown [skip ci]

lntest/harness_net.go

@@ -266,8 +266,12 @@ func (n *NetworkHarness) Stop() {
 	close(n.lndErrorChan)
 	n.cancel()
 
+	// feeService may not be created. For instance, running a non-exist
+	// test case.
+	if n.feeService != nil {
 		n.feeService.stop()
 	}
+}
 
 // extraArgsEtcd returns extra args for configuring LND to use an external etcd
 // database (for remote channel DB and wallet DB).