Should not allow saving invalid visitor group

Description

Steps to reproduce

1. Make sure that ClientLocationHeader is NOT configured in code and web.config.
2. Create a 'Geographic location' VG that has a region value.
3. Remove the Geolocation provider settings from code and web.config.
4. Open the VG -> The VG indicates the error.
5. Click the 'Save' button.

Expected:
Cannot save the value because the VG is invalid.

Actual:
You can successfully save the VG that has no field value. When opening the VG again, we see no error message for the invalid VG.