Fix blank sidebar items when linkTitle/title is missing

[priyankajainibmz]

Fixes #720

Changes

Fixes an issue where some sidebar items were rendered as blank (clickable but with no visible text).

This occurred when linkTitle and title were missing in certain synced documentation pages.

Added a fallback in the sidebar template:

• Use .LinkTitle if available
• Else .Title
• Else fallback to .File.BaseFileName

This ensures all sidebar items are visible even when metadata is missing.

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• ✅ login: priyankajainibmz / name: Priyanka Jain (97bf5b0)