Not sure if you are still having the issue, but if anyone else encounters this problem this is how I reverted the changes:
1. Navigate to the URL that is the System Settings page of the controller (it is just the dashboard URL that is broken):
https://[ControllerIP]/admin10/conf_system.jsp2. Scroll to the bottom and clear the Configure Map section of the API key you put in
3. Apply the changes and try the dashboard page again.