exp/rvcl: remove nil option from netsender

This was a programmer's mistake.

Approved-by: Alan Noble

exp/rvcl/main.go

@@ -207,7 +207,7 @@ func main() {
 
 	// Create a netsender client. This is used only for HTTP sending of media
 	// in this binary.
-	ns, err := netsender.New(log, nil, nil, nil, nil)
+	ns, err := netsender.New(log, nil, nil, nil)
 	if err != nil {
 		log.Fatal("could not initialise netsender client", "error", err)
 	}