Redirect loop on Make when visiting wp-admin over HTTP without a user role

If a logged-in user attempts to visit /wp-admin over HTTP on some Make sites that they don’t have access to, they get stuck in a redirect loop.

It doesn’t affect all of the sites, though, and it doesn’t happen if they request it over HTTPS.

e..g, requesting https://make.wordpress.org/training/wp-admin redirects to https://make.wordpress.org/training/wp-admin/edit.php?post_type=handbook and then fails.

I’m seeing it on /training, /docs, /core, and /meta, but not on /community. I didn’t test beyond that, though.