build: fix build failure

_includes/toc-status.html

@@ -0,0 +1,10 @@
+{% comment %}
+  Determine TOC state and return it through variable "enable_toc"
+{% endcomment %}
+
+{% assign enable_toc = false %}
+{% if site.toc and page.toc %}
+  {% if page.content contains '<h2' or page.content contains '<h3' %}
+    {% assign enable_toc = true %}
+  {% endif %}
+{% endif %}