cmd/swarm: ethapi not required

cmd/swarm/main.go

@@ -254,14 +254,12 @@ func registerBzzService(ctx *cli.Context, stack *node.Node) {
 
 	boot := func(ctx *node.ServiceContext) (node.Service, error) {
 		var client *ethclient.Client
-		if ethapi == "" {
-			err = fmt.Errorf("use ethapi flag to connect to a an eth client and talk to the blockchain")
-		} else {
+		if len(ethapi) > 0 {
 			client, err = ethclient.Dial(ethapi)
-		}
 			if err != nil {
 				utils.Fatalf("Can't connect: %v", err)
 			}
+		}
 		return swarm.NewSwarm(ctx, client, bzzconfig, swapEnabled, syncEnabled)
 	}
 	if err := stack.Register(boot); err != nil {