fix(song): handle empty SNG_CONTRIBUTORS array during unmarshal

internal/deezer/song.go

@@ -1,22 +1,37 @@
 package deezer
 
 import (
+	"encoding/json"
 	"fmt"
 
 	"github.com/flytam/filenamify"
 )
 
+type Contributors struct {
+	MainArtists []string `json:"main_artist"`
+	Composers   []string `json:"composer"`
+	Authors     []string `json:"author"`
+}
+
+func (c *Contributors) UnmarshalJSON(data []byte) error {
+	if string(data) == "[]" {
+		*c = Contributors{}
+		return nil
+	}
+
+	type Alias Contributors
+	aux := (*Alias)(c)
+
+	return json.Unmarshal(data, aux)
+}
+
 type Song struct {
 	ID           string       `json:"SNG_ID"`
 	Artist       string       `json:"ART_NAME"`
 	Title        string       `json:"SNG_TITLE"`
 	Version      string       `json:"VERSION"`
 	Cover        string       `json:"ALB_PICTURE"`
-	Contributors struct {
+	Contributors Contributors `json:"SNG_CONTRIBUTORS"`
-		MainArtists []string `json:"main_artist"`
-		Composers   []string `json:"composer"`
-		Authors     []string `json:"author"`
-	} `json:"SNG_CONTRIBUTORS"`
 	Duration     string       `json:"DURATION"`
 	Gain         string       `json:"GAIN"`
 	ISRC         string       `json:"ISRC"`