/help/: Fix sidebar target bug.

This tries to toggle the next item when clicking on an <h2>
in the sidebar, however we want to first check the next item is
an <ul> element, so that we are collapsing or showing a list,
instead of something like an <h2> which currently happens with
the "#guides" element.

static/js/portico/help.js

@@ -14,7 +14,11 @@
     };
 
     $(".sidebar h2").click(function (e) {
-        $(e.target).next().slideToggle('fast');
+        var $next = $(e.target).next();
+
+        if ($next.is("ul")) {
+            $next.slideToggle("fast");
+        }
     });
 
     $(".sidebar a").click(function (e) {