Check value to not be null

[k-bx]

Not sure how to test this locally, couldn't find "hacking" doc. Asked on Slack.

[lukewestby]

@k-bx can you open an issue instead? I don't think function should ever see null so the fix might be more complicated and potentially involve the compiler.

[evancz]

Yes, please open an issue with an http://sscce.org/

[k-bx]

Done in https://github.com/elm/compiler/issues/1856 . I believe this fix is correct. The offender code is doing Date.prototype._nth = null and it breaks things (introducing a null "object"). Also, I've tested this patch and it works well.