Fix crash after connection closure.

app/channels/channel.go

@@ -56,6 +56,7 @@ func (channel *Channel) SetMetadata(data map[string]string) {
 func (channel *Channel) Metadata() chan map[string]string {
 	outC := make(chan map[string]string)
 	go func() {
+		defer close(outC)
 		c := channel.Events.Sub("metadata")
 	forloop:
 		for event := range c {

plugins/icecast/output/instance.go

@@ -75,7 +75,7 @@ func (instance *pluginInstance) Init() {
 			nw = mw
 
 			metadataChan := channel.Metadata()
-			defer close(metadataChan)
+			defer func() { metadataChan <- nil }()
 			go func() {
 				for metadata := range metadataChan {
 					metadataToWrite := streams.Metadata{}