PostgreSQL with unavailable parameter in function

I have this function built using PostgreSQL:

CREATE OR REPLACE FUNCTION "db"."t_pencabutan_likuidasi_after_update"()
  RETURNS "pg_catalog"."trigger" AS $BODY$
BEGIN
    IF(NEW.status <> OLD.status) THEN
        INSERT INTO 
             t_pencabutan_likuidasi_log(id_pencabutan, id_profile, nama_petugas, nip_petugas, status, catatan)
        VALUES(
             NEW.id_pencabutan, NEW.id_profile, NEW.nama_petugas, NEW.nip_petugas, NEW.status, NEW.catatan);
    END IF;
        RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100

Above is a function that will triggered BEFORE UPDATE of the table liquidator.

The problem is some of the fill on the INSERT were not mandatory inserted, like nama_petugas and nip_petugas which is a temporary value. Sometimes it is inserted, but sometimes it isn't. It gives an error like this:

ERROR:  record "new" has no field "nama_petugas"

How could I leave it blank when there is no value/variable that is inserted for nama_petugas and nip_petugas?

Here is my trigger function;

CREATE TRIGGER 
"t_pencabutan_likuidasi_after_update" 
AFTER UPDATE OF "status" 
ON "db"."liquidator"
FOR EACH ROW
EXECUTE PROCEDURE 
"db"."t_pencabutan_likuidasi_after_update"();