[keycloak-user] No Default theme - Null Pointer Exception

Hi All: My use case was to automatically direct the user to a custom theme depending on the device they are using e.g: native mobile vs other. The theme selector will make a decision based on User Agent and direct the end-user accordingly. I created a theme selector based on the source code snippets provided from https://www.keycloak.org/docs/latest/server_development/index.html#_provi.... I basically did a copy and paste. I was able to deploy the theme and it appeared in the Provider's tab in the Admin console. I copied the base theme as 'my-theme'. When I restart the Keycloak server it fails to start throwing an NPE indicating that there is No Default theme. I was wondering if I needed any other code or configuration that is not stated in that particular section to get this going? I couldn't find a working sample online, so if I can be directed to one that would be great. Thanks a bunch! Chuck.