doc: prevent displaying empty version picker

PR-URL: https://github.com/nodejs/node/pull/15420
Fixes: https://github.com/nodejs/node/issues/15396
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

tools/doc/html.js

@@ -232,9 +232,17 @@ function altDocs(filename) {
     return html + '</a></li>';
   }
 
-  const lis = (vs) => vs.filter(lte).map(li).join('\n');
+  const lis = versions.filter(lte).map(li).join('\n');
 
-  return `<ol class="version-picker">${lis(versions)}</ol>`;
+  if (!lis.length)
+    return '';
+
+  return `
+    <li class="version-picker">
+      <a href="#">View another version <span>&#x25bc;</span></a>
+      <ol class="version-picker">${lis}</ol>
+    </li>
+  `;
 }
 
 // handle general body-text replacements