Fix javascript hacks for oxygen 1.8.13
diff --git a/doc/eigen_navtree_hacks.js b/doc/eigen_navtree_hacks.js
index bd7e02b..39c59f7 100644
--- a/doc/eigen_navtree_hacks.js
+++ b/doc/eigen_navtree_hacks.js
@@ -65,6 +65,10 @@
 function resizeHeight() 
 {
   var toc = $("#nav-toc");
+  var header = $("#header");
+  var content = $("#doc-content");
+  var navtree = $("#nav-path");
+  var sidenav = $("#side-nav");
   var tocHeight = toc.height();  // <- we added this line
   var headerHeight = header.height();
   var footerHeight = footer.height();