Airtable offers the option to do a destructive update, so if a field is not specified in the fields you send, it is automatically set to null. Implement this feature per their documentation:
To update referrals records, issue a request to the referrals endpoint. A PATCH request will only update the fields you specify, leaving the rest as they were. A PUT request will perform a destructive update and clear all unspecified cell values. The example at the right uses the non-destructive PATCH method
Airtable offers the option to do a destructive update, so if a field is not specified in the fields you send, it is automatically set to null. Implement this feature per their documentation: