MapStruct does not parse env, when mapping all data

[mbretter]

System (please complete the following information):

• OS: linux
• GO Version: 1.22.4
• Pkg Version: 2.2.3

Describe the bug

When using MapStruct with empty key, i.e. mapping all, no environment variables are parsed

To Reproduce

	cfg := Config{}
	err = ini.MapStruct("", &cfg)
	fmt.Println(cfg.MongoDb,Uri)

	x := ini.String("mongodb.uri")
	fmt.Println(x)

	mcfg := MongoDb{}
	ini.MapStruct("mongodb", &mcfg)
	fmt.Println(mcfg)

output:

${MONGO_URI}
mongodb://xxx:[email protected]/mydb
mongodb://xxx:[email protected]/mydb

Expected behavior

Environment variables must be parsed