Received a notice from Google Adsense that I need to remove their ad code on the login page because it doesn't contain any content. 

Is there a way to disable ad serving on a single page?

When you setup Adsense using ACP -> Advertisements did you make sure this setting was disabled?

These are the only two options I am seeing in Advertisement Settings. I haven't done the latest update. Will do it now. 

 

This would be on your advertisement itself, not the global setting. So go to ACP -> System -> Advertisements -> edit your advertisement.

If you’re using Auto Ads, you can exclude a page from with the Google Adsense interface. 
 

https://support.google.com/adsense/answer/9262311?hl=en