Set add/edit record metadata item to optional

Is it possible in an add or edit record database request to set specific metadata fields ( the mapping of the input to the database field ) to be optional, so that if the calling system does not pass that specific key through, the request will just ignore it?

I've tried using first_notempty for this purpose (as per screenshot), however Xano still requires that all var's mentioned in the metadata mapping exist otherwise an error will be thrown. [MetadataMapping.png]The payload from my calling system will differ from call to call, but I still want to map an input if it does exist to a field in the database, so I can't take it out.

Thanks for any advice.