We move the getPRFromComment to an upper function in this commit: https://github.com/mattermost/mattermost-mattermod/commit/9cc7d319e10a1f80d604041ec7425d043fe6bbe2
It is crashing because sometimes `*comment.Issue` is a nil field.
handleAutoAssign never really called PullRequests.Get. It called s.GithubClient.Repositories.ListTeams, so a nil `Issue` field didn't bother it.
We need to properly parse the GitHub response and decide which handler to call depending on it.
No testing required.