Looking for a Default Value for Geographic Address field

In my tblVenues, I’ve got a field for tblVenueAddress which is set to a Geographic Address type.
It works well but when I try to show this venue on a map (using Google Maps BDK) the marker will only display if ALL the entries in the field are complete - ie if it isn’t blank. This is a problem because when I select users, I want the map to show a marker for each selected User’s Favourite Venue. If just one of my Users has an empty value for that field, none of the markers display for any of the selected users because it causes an error. So I’m thinking a default value in the field would avoid this but this would require a sample postcode and that then leads to its own issues. Is there a standard way around this?