fix artistid

main.go

@@ -818,6 +818,7 @@ func writeM4a(w *mp4.Writer, info *SongInfo, meta *AutoGenerated, data []byte, t
 						}
 					}
 
+					if len(meta.Data[0].Relationships.Tracks.Data[index].Relationships.Artists.Data) > 0 {
 						if len(meta.Data[0].Relationships.Tracks.Data[index].Relationships.Artists.Data[0].ID) > 0 {
 							atID, err := strconv.ParseUint(meta.Data[0].Relationships.Tracks.Data[index].Relationships.Artists.Data[0].ID, 10, 32)
 							if err != nil {
@@ -829,6 +830,7 @@ func writeM4a(w *mp4.Writer, info *SongInfo, meta *AutoGenerated, data []byte, t
 								return err
 							}
 						}
+					}
 					trkn := make([]byte, 8)
 					disk := make([]byte, 8)
 					binary.BigEndian.PutUint32(trkn, uint32(meta.Data[0].Relationships.Tracks.Data[index].Attributes.TrackNumber))

main_select.go

@@ -812,7 +812,7 @@ func writeM4a(w *mp4.Writer, info *SongInfo, meta *AutoGenerated, data []byte, t
 							}
 						}
 					}
-
+					if len(meta.Data[0].Relationships.Tracks.Data[index].Relationships.Artists.Data) > 0 {
 						if len(meta.Data[0].Relationships.Tracks.Data[index].Relationships.Artists.Data[0].ID) > 0 {
 							atID, err := strconv.ParseUint(meta.Data[0].Relationships.Tracks.Data[index].Relationships.Artists.Data[0].ID, 10, 32)
 							if err != nil {
@@ -824,6 +824,7 @@ func writeM4a(w *mp4.Writer, info *SongInfo, meta *AutoGenerated, data []byte, t
 								return err
 							}
 						}
+					}
 					trkn := make([]byte, 8)
 					disk := make([]byte, 8)
 					binary.BigEndian.PutUint32(trkn, uint32(meta.Data[0].Relationships.Tracks.Data[index].Attributes.TrackNumber))