Why should websocket be destroyed when getting LWS_CALLBACK_CLIENT_WRITEABLE?

[klauski]

When socket become writeable, runtime error rises because web client go to be destroyed..

The related code is in scclient.cpp,
if (writeable_flag)
destroy_flag = 1; <= raise problem
}
break;
case LWS_CALLBACK_CLIENT_WRITEABLE :{
// printf(KYEL"[Main Service] On writeable is called. send byebye message\n"RESET_);
websocket_write_back(wsi, (char *)"Byebye! See you later", -1);
writeable_flag = 1;