Subpage divider and selector appears even though there are no subpages

[ericokuma]

Describe the bug
As a user who is only a viewer on demo projects, I see the subpage divider and it's highlighted selector even though there are no subpages

To Reproduce
Steps to reproduce the behavior:

1. rill sudo user assume [email protected]
2. rill sudo user open
3. See the issue

Expected behavior
No subpage divider and highlighted selector when there are no subpages

Screenshots
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Desktop (please complete the following information):

• OS: MACOS
• Browser: Safari
• Version: Version 18.3 (20620.2.4.11.5)

Additional context
Add any other context about the problem here.