fix jumping navbar

layouts/partials/header.html

@@ -41,6 +41,7 @@
         <div id="overlay"></div>
         <div class="padding highlightable sticky-parent">
               {{if not .IsHome}}
+              <div class="sticky-spacer">
                 <div id="top-bar">
                 {{ if and (or .IsPage .IsSection) .Site.Params.editURL }}
                   {{ $File := .File }}
@@ -72,6 +73,7 @@
                     {{ partial "toc.html" . }}
                 {{ end }}
               </div>
+            </div>
             {{ end }}
 
         {{ if .Params.chapter }}