fix issue in empty slice converting panic for gconv.Struct

.example/other/test.go

@@ -1,19 +1,48 @@
 package main
 
 import (
+	"github.com/gogf/gf/encoding/gjson"
 	"github.com/gogf/gf/frame/g"
-	"github.com/gogf/gf/net/ghttp"
+	"github.com/gogf/gf/util/gconv"
 )
 
-func main() {
-	s := g.Server()
-	s.SetIndexFolder(true)
-	s.BindHandler("/admin.html", func(r *ghttp.Request) {
-		r.Response.Write("admin")
-	})
-	s.BindHandler("/admin-do-{page}.html", func(r *ghttp.Request) {
-		r.Response.Write("admin-do-" + r.GetString("page"))
-	})
-	s.SetPort(8999)
-	s.Run()
+//
+type BaseData struct {
+	Title     string `json:"title"`
+	Content   string `json:"content"`
+	BeginTime int64  `json:"begin_time"`
+	EndTime   int64  `json:"end_time"`
+}
+
+// 奖励数据
+type RewardOneData struct {
+	Type  string `json:"type"`
+	Id    uint32 `json:"id"`
+	Count uint32 `json:"count"`
+}
+
+// 邮件
+type MailOneData struct {
+	Base       BaseData        `json:"base"`
+	MailId     uint32          `json:"mail_id"`
+	PicId      uint32          `json:"pic_id"`
+	PlayerList g.ArrayStr      `json:"player_list"`
+	Reward     []RewardOneData `json:"reward"`
+}
+
+func main() {
+	test()
+}
+
+func test() {
+	// 使用下面这行就会panic 原因是 最后的reward字段列表为空
+	jsonStr := "{\"base\":{\"title\":\"testTitle\",\"content\":\"testContent\",\"begin_time\":1574763804,\"end_time\":1574767404},\"mail_id\":1,\"pic_id\":1,\"player_list\":[],\"reward\":[]}"
+	//jsonStr := "{\"base\":{\"title\":\"testTitle\",\"content\":\"testContent\",\"begin_time\":1574763804,\"end_time\":1574767404},\"mail_id\":1,\"pic_id\":1,\"player_list\":[],\"reward\":[{\"type\":\"diamond\",\"id\":0,\"count\":100}]}"
+	decodeData, _ := gjson.Decode(jsonStr)
+
+	decodeMailData := new(MailOneData)
+	gconv.Struct(decodeData, decodeMailData)
+
+	//
+	g.Dump(decodeMailData)
 }