Preconditions:

Created Content Type which is not a container.

Steps:

1. Go to Content/Content structure
2. Click Create and choose CT from preconditions
3. Publish it
4. Click Page/site to see page preview of created content item
5. Click [+] button and choose Landing Page
6. Fill required fields and publish Landing Page

Actual result:

LP is published and it is a child of non container CI.

Expected result:

Create button should be disabled as it is when user goes to preview of CI from Content structure.