I can't initialize to empty a field (Lat, Lng) in a Firebase table

Hello,

I have a field (Lat, Lng) in a Firebase table that I can't *initialize to empty from an action query. The null value causes an error and from the database (Firestore Data Manager) I can't delete this field with an update. The idea is to be able to do this* from my application.

The only possibility I've found (but which doesn't satisfy me) is to use the "Current Device Location" value in my "Backend Call Update Document". This sets Lat = 0 and Lng = 0 in the database. That's the location in blue in the image, but I'd like to have nothing in this field, as below the blue image.

Any ideas?