Bug: req.session.id where session is undefined

[xinbenlv]

/home/user/ws/wikiloop-battlefield/server/index.ts:69
        session_id: req.session.id
                                ^
TypeError: Cannot read property 'id' of undefined
    at ServerResponse.<anonymous> (/home/zzn_google/ws/wikiloop-battlefield/server/index.ts:69:33)
    at ServerResponse.emit (events.js:224:7)
    at ServerResponse.EventEmitter.emit (domain.js:482:12)
    at onFinish (_http_outgoing.js:722:10)
    at onCorkedFinish (_stream_writable.js:739:5)
    at afterWrite (_stream_writable.js:537:5)
    at afterWriteTick (_stream_writable.js:524:10)
    at processTicksAndRejections (internal/process/task_queues.js:83:21)