Left-hand navigation pane does not render if deeper link is followed

[dcamper]

The following problem does not appear if you start at the beginning of the site and navigate using controls.

If you go to a topic and bookmark it (e.g. https://learn.hpccsystems.com/hpcc/Tutorial/ECLSyntax/bigData), then return to that page via the bookmark later, the left-hand navigation pane does not render. You can duplicate the problem by instead simply copying the URL and pasting it into a new tab.