Handle ghost users - users who are no longer in the org

[dnorth98]

TIL that when a user leaves the org, deploys are assigned to the "Ghost" user! The triggering_actor becomes empty

'triggering_actor': None,

and everything becomes assigned to this special GH user called "ghost"

{'actor': {'avatar_url': 'https://avatars.githubusercontent.com/u/10137?v=4',
           'events_url': 'https://api.github.com/users/ghost/events{/privacy}',
           'followers_url': 'https://api.github.com/users/ghost/followers',
           'following_url': 'https://api.github.com/users/ghost/following{/other_user}',
           'gists_url': 'https://api.github.com/users/ghost/gists{/gist_id}',
           'gravatar_id': '',
           'html_url': 'https://github.com/ghost',
           'id': 10137,
           'login': 'ghost',
           'node_id': 'MDQ6VXNlcjEwMTM3',
           'organizations_url': 'https://api.github.com/users/ghost/orgs',
           'received_events_url': 'https://api.github.com/users/ghost/received_events',
           'repos_url': 'https://api.github.com/users/ghost/repos',
           'site_admin': False,
           'starred_url': 'https://api.github.com/users/ghost/starred{/owner}{/repo}',
           'subscriptions_url': 'https://api.github.com/users/ghost/subscriptions',
           'type': 'User',
           'url': 'https://api.github.com/users/ghost',
           'user_view_type': 'public'},