Cleanup the Javascript and CSS of our custom TOC

Author: Urgau

src/doc/rustc/theme/pagetoc.css

@@ -10,14 +10,6 @@
 min-width:50px;
 }
 
-.previous {
-/*
- adjust the space between the left sidebar or the left side of the screen 
- and the button that leads to the previous page
- */
-margin-left:var(--page-padding);
-}
-
 @mediaonly screen {
 @media (max-width:1179px) {
  .sidebar-hidden#sidetoc {

src/doc/rustc/theme/pagetoc.js

@@ -71,7 +71,8 @@ function updatePageToc(elem = undefined) {
 }
 }
 
-if(document.getElementById("sidetoc")===null){
+if(document.getElementById("sidetoc")===null&&
+document.getElementsByClassName("header").length>0){
 // The sidetoc element doesn't exist yet, let's create it
 
 // Create the empty sidetoc and pagetoc elements
@@ -80,16 +81,11 @@ if (document.getElementById("sidetoc") === null) {
 sidetoc.id="sidetoc";
 pagetoc.id="pagetoc";
 sidetoc.appendChild(pagetoc);
-
+
 // And append them to the current DOM
 constmain=document.querySelector('main');
 main.insertBefore(sidetoc,main.firstChild);
-}
 
-if(document.getElementsByClassName("header").length<=1){
-// There's one or less headings, we don't need a page table of contents
-document.getElementById("sidetoc").remove();
-}else{
 // Populate sidebar on load
 window.addEventListener("load",()=>{
 for(constheaderofdocument.getElementsByClassName("header")){