AP.content.getContext() returns an empty object in dynamic content macro editors

Issue Summary

AP.content.getContext() returns an empty object in dynamic content macro editors.

Steps to Reproduce

1. Create an app with a dynamic content macro defining a custom editor.
2. Open the editor and call AP.context.getContext(callback)

Expected Results

The callback is called with a context object similar to:

confluence: {
  content: {
    id: "12345678"
    type: "page"
    version: "7"
  }
  macro: {
    hash: "58e722af-f259-41be-a8df-ddddddd"
    id: "58e722af-f259-41be-a8df-eeeeeeee"
  }
  space: {
    id: "1234567"
    key: "FOO"
  }
}

Actual Results

The context object is empty (for an unlicensed app):

{}

Workaround

This might be a reasonable workaround https://community.developer.atlassian.com/t/attaching-a-file-via-restapi-to-a-confluence-page-draft/46609/11