example case crash

[fastfading]

~/go/bin/gotube -d -id C0DPdy98e4c -q medium -ext video/mp4
panic: interface conversion: interface {} is nil, not string

goroutine 1 [running]:
github.com/KeluDiao/gotube/api.GetVideoListFromJson(0xc00008fe90, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x2b)
/Users/xxx/go/src/github.com/KeluDiao/gotube/api/analyzer.go:54 +0x9b2
github.com/KeluDiao/gotube/api.GetVideoListFromUrl(0xc000128000, 0x2b, 0x0, 0x0, 0x0, 0x0, 0x0, 0xc0000bab50, 0x203000)
/Users/xxx/go/src/github.com/KeluDiao/gotube/api/http.go:47 +0xa1
github.com/KeluDiao/gotube/api.GetVideoListFromId(...)
/Users/xxx/go/src/github.com/KeluDiao/gotube/api/http.go:29
main.main()
/Users/xxx/go/src/github.com/KeluDiao/gotube/script.go:75 +0xc72