fix: explicit undefined check in header transclude

Jacky Zhao

2023-11-19 516d9a27e7e2c08efdf24857b03f1831dbaf7da7

 docs/features/OxHugo compatibility.md

@@ -32,6 +32,7 @@
  - `replaceFigureWithMdImg`: Whether to replace `<figure/>` with `![]()`
- Formatting
  - `removeHugoShortcode`: Whether to remove hugo shortcode syntax (`{{}}`)
  - `replaceOrgLatex`: Whether to replace org-mode formatting for latex fragments with what `Plugin.Latex` supports.

> [!warning]
>