Handle case where artists value is a single string rather than a slice. Fixes Arsen6331/itd#9.

pkg/player/player.go

@@ -163,12 +163,17 @@ func OnChange(cb func(ChangeType, string)) {
 							}
 							cb(ChangeTypeAlbum, album)
 						} else if strings.HasSuffix(name, "artist") {
-							artists := val.Value().([]string)
-							artistStr := strings.Join(artists, ", ")
-							if artistStr == "" {
-								artistStr = "Unknown " + ChangeTypeArtist.String()
+							var artists string
+							switch artistVal := val.Value().(type) {
+							case string:
+								artists = artistVal
+							case []string:
+								artists = strings.Join(artistVal, ", ")
 							}
-							cb(ChangeTypeArtist, artistStr)
+							if artists == "" {
+								artists = "Unknown " + ChangeTypeArtist.String()
+							}
+							cb(ChangeTypeArtist, artists)
 						}
 					}
 				} else if name == "PlaybackStatus" {