prevent broken updates when no master is set

node/icecast.go

 package node
 
 import (
+	"errors"
+	"log"
 	"os"
 	"os/exec"
 )
@@ -30,6 +32,11 @@ func (ic *IcecastController) reload() error {
 }
 
 func (ic *IcecastController) Update(conf *ClusterConfig, isMaster bool, masterAddr string) error {
+	if !isMaster && masterAddr == "" {
+		log.Printf("system in unknown state (no master) - update aborted")
+		return errors.New("unknown system state")
+	}
+
 	tmpf := ic.ConfigFile + ".tmp"
 	defer os.Remove(tmpf)