A presence update can sometimes kill the discord bot

[brianpeiris]

It seems a particular type of presence update can kill the discord bot, forcing it to restart:

TypeError: Cannot read property 'kind' of null
    at PresenceRollups.rename (/hab/svc/hubs-discord-bot/static/src/presence-rollups.js:84:56)
    at ReticulumChannel.<anonymous> (/hab/svc/hubs-discord-bot/static/src/presence-rollups.js:49:71)
    at ReticulumChannel.emit (events.js:209:13)
    at ReticulumChannel.EventEmitter.emit (domain.js:476:20)
    at /hab/svc/hubs-discord-bot/static/src/reticulum.js:46:16
    at /hab/svc/hubs-discord-bot/static/node_modules/phoenix/priv/static/phoenix.js:1:21521
    at /hab/svc/hubs-discord-bot/static/node_modules/phoenix/priv/static/phoenix.js:1:21942
    at Array.map (<anonymous>)
    at Function.value (/hab/svc/hubs-discord-bot/static/node_modules/phoenix/priv/static/phoenix.js:1:21919)
    at Function.value (/hab/svc/hubs-discord-bot/static/node_modules/phoenix/priv/static/phoenix.js:1:21325)