Hey Im currently getting this error. I'm at the  05:21min in the tutorial

application.js:267 Error connecting controller

TypeError: Cannot read property '__k' of undefined
    at S (preact.module.js:343)
    at DelayedRunner.Calendar._this.handleRenderRequest [as drainedOption] (main.js:46)
    at DelayedRunner.drained (main.js:8347)
    at DelayedRunner.tryDrain (main.js:8325)
    at DelayedRunner.request (main.js:8274)
    at Calendar.render (main.js:103)
    at extended.connect (calendar_controller.js:20)
    at Context.connect (context.js:24)
    at Module.connectContextForScope (module.js:37)
    at Router.scopeConnected (router.js:112)

How do I fix this?