[Bug] PDF Download not appearing for nested TOC

**Describe the bug**
Using nested TOCs the Download PDF is not available. The PDF files are correctly generated. The download PDF option appears only when the master TOC has PDF generation enabled.

**To Reproduce**
Content of docfx.json:

> "globalMetadata": {
> "pdfTocPage": true
> }

Content of the master TOC:

> items:
> - name: Italian Bank Integration
> href: ItalianBankIntegration/toc.yml
> homepage: ItalianBankIntegration/intro.md

Content of the nested TOC:

> pdf: true
> pdfFileName: ItalianBankIntegration.pdf
> pdfCoverPage: covers/ItalianBankIntegration.html
> href: intro.md
> items:
> - name: XXX
> href: XXX.md

The template is **modern**.

**Expected behavior**
The PDF Download option should appear in the bottom left area when selecting the menu area related to this TOC.

**Context (please complete the following information):**
- OS: Windows
- Docfx version: 2.77.0

Reproduce the issue with the supplied docfx.json, master TOC, nested toc.yml, and modern template on DocFX 2.77.0. Compare navigation rendering for the master and nested TOCs; done when the PDF download option appears in the bottom-left menu for the nested TOC while its generated PDF remains available.

Written by the indexing model from the issue text.