Fix wrong anchors

While experimenting with the ToC changes, it became obvious that anchors
for those unnamed headers don't work.

This patch fixes those links by running the autolinkify twice and make
sure linkify only adds links to non-empty ids.

Signed-off-by: Sheogorath <sheogorath@shivering-isles.com>

public/js/index.js

@@ -2786,6 +2786,7 @@ function updateViewInner () {
   renderTOC(ui.area.markdown)
   generateToc('ui-toc')
   generateToc('ui-toc-affix')
+  autoLinkify(ui.area.markdown)
   generateScrollspy()
   updateScrollspy()
   smoothHashScroll()