Doc Theme breaks if JavaScript not served in header

To reproduce:

1. Turn off serving JavaScript in header via Confluence Admin > General Configuration > Feature Settings > JavaScript served in header
2. Go to any space and select the Documentation Theme
3. Reload the page

The sidebar will load incorrectly at the top of the page, and the following JavaScript error will be reported:

AJS is not defined
http://localhost:8080/s/2032/1/1.6/_/download/resources/com.atlassian.confluence.plugins.doctheme:resources/doc-theme.js
Line 205