custom Nice menus CSS file not injected into document head

After copying the default file to my themes folder, setting the path to the custom CSS file, and saving the new settings (both on the theme under development and globally), the module failed to apply the stylesheet to the document.

Steps taken:
Link color and additional styling was default blue, regardless of changes applied to custom CSS. Upon examining the page source after setting custom CSS path, I noticed the document did not include a script tag in the head with a reference to custom CSS. This was verified by applying all changes to nice_menus.css, after which all the modifications appeared. Since modification to nice_modules.css is obviously not intended, and the only fix is to hack it, this is definitely broken.