Fix a couple bugs. (#6313)

- Set the right style for the auto-inserted header links. Without this,
they didn't render correctly with the Edge browser.

- Fix broken Hugo error message, leading to broken builds if
encountered.

Co-authored-by: Martin Taillefer <geeknoid@users.noreply.github.com>

layouts/partials/code_block.html

@@ -59,7 +59,7 @@
     {{- end -}}
 
     {{- if (hasPrefix $text " ") -}}
-        {{- errorf "Text blocks need to not be indented, or indented by a multiple of 4 spaces (%s)" .Page.Position -}}
+        {{- errorf "Text blocks need to not be indented, or indented by a multiple of 4 spaces (%s)" .Position -}}
     {{- end -}}
 
     {{- if $snippet -}}

src/sass/base/_base.scss

@@ -264,7 +264,7 @@ h6 {
 
 @media screen {
     .self-link {
-        display: unset;
+        display: inline;
     }
 }