Panic on session.ChannelVoiceJoin in deafened=false mode

[khodand]

goroutine 89 [running]:
github.com/bwmarrin/discordgo.(*VoiceConnection).opusReceiver(0xc0004154a0, 0xc000092130, 0xc0000949c0, 0xc000176360)
        ***/vendor/github.com/bwmarrin/discordgo/voice.go:837 +0x59a
created by github.com/bwmarrin/discordgo.(*VoiceConnection).onEvent
       ***/vendor/github.com/bwmarrin/discordgo/voice.go:441 +0x6d8

I'm creating a music bot. When bot catch's the message event, it is initializing the voice connection. The bot connects to the voice channel, and after that it can accidentally throw a panic.

Connnecting:

// (s *discordgo.Session, m *discordgo.MessageCreate)
        guild, err := s.State.Guild(m.GuildID)
	if err != nil {
		return "", err
	}
	id := ""
	for _, voiceState := range guild.VoiceStates {
		if voiceState.UserID == m.Author.ID {
			id = voiceState.ChannelID
			break
		}
	}
	c.session.ChannelVoiceJoin(m.GuildID, id, false, false)

[khodand]

session.Open() was successful

There seems to be a panic when calling ChannelVoiceJoin()
The (s *Session) ChannelVoiceJoinManual calls for a s.wsConn, but s.wsConn == nil

runtime.fatalpanic (panic.go:1271) runtime
runtime.gopanic (panic.go:1147) runtime
runtime.panicmem (panic.go:221) runtime
runtime.sigpanic (signal_windows.go:254) runtime
websocket.(*Conn).beginMessage (conn.go:479) github.com/gorilla/websocket
websocket.(*Conn).NextWriter (conn.go:520) github.com/gorilla/websocket
websocket.(*Conn).WriteJSON (json.go:24) github.com/gorilla/websocket
discordgo.(*Session).ChannelVoiceJoinManual (wsapi.go:722) github.com/bwmarrin/discordgo
discordgo.(*Session).ChannelVoiceJoin (wsapi.go:684) github.com/bwmarrin/discordgo