No actions UI for Tag field in new Post form creation

[simonswiss]

When spinning up a new Keystone app with create-keystone-app, without changing anything to the code, it's impossible to add a Tag on the Post creation form.

Only the field legend shows, no other UI:

An empty span is rendered below the legend:

This only happens on "new post" side-panel form. When editing an existing post it's possible to create or connect tags to the post:

Steps to reproduce

1. Create a new Keystone project with create-keystone-app
2. Start the dev server
3. Create a new post, and try to add a tag to that post directly from the new post form