undefined variable "$firstBracket" when running server

I got the following error when running the server on a PaperMod theme.

parse failed: template: partials/content-wikilinks.html:16: undefined variable "$firstBracket"

Not sure if I have installed it properly.

tree layouts:

layouts
├── _default
│   └── single.html
└── partials
├── content-wikilinks.html
├── funcs
│   └── backlinks.html
├── LICENSE
└── README.md

3 directories, 5 files

tree themes/PaperMod/layouts:

themes/PaperMod/layouts
├── 404.html
├── _default
│   ├── archives.html
│   ├── baseof.html
│   ├── index.json
│   ├── list.html
│   ├── _markup
│   │   └── render-image.html
│   ├── rss.xml
│   ├── search.html
│   ├── single.html
│   └── terms.html
├── partials
│   ├── anchored_headings.html
│   ├── author.html
│   ├── breadcrumbs.html
│   ├── comments.html
│   ├── cover.html
│   ├── edit_post.html
│   ├── extend_footer.html
│   ├── extend_head.html
│   ├── footer.html
│   ├── header.html
│   ├── head.html
│   ├── home_info.html
│   ├── index_profile.html
│   ├── post_canonical.html
│   ├── post_meta.html
│   ├── post_nav_links.html
│   ├── share_icons.html
│   ├── social_icons.html
│   ├── svg.html
│   ├── templates
│   │   ├── opengraph.html
│   │   ├── schema_json.html
│   │   └── twitter_cards.html
│   ├── toc.html
│   └── translation_list.html
├── robots.txt
└── shortcodes
├── collapse.html
├── figure.html
├── inTextImg.html
├── ltr.html
├── rawhtml.html
└── rtl.html

I think I know why...

{ $firstBracket := "\\[\\[" }}

This definition on content-wikilinks.html is missing an opening curly brace.