Re: [GENERAL] ERROR: unexpected chunk number 0 (expected 1) for toastvalue 76753264 in pg_toast_10920100

I am new to postgress and I am trying to write my first function to insert, update or delete and trap errors as a result of the table not existing , the columns not exist or if any other error simply pass back the sqlstate here's my code can you help
CREATE OR REPLACE FUNCTION listings_audit() RETURNS TRIGGER AS
$listings_audit$
  BEGIN
    IF (TG_OP = 'DELETE') THEN
     IF (EXISTS (
          SELECT 1
          FROM pg_catalog.pg_class c
          JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
          WHERE n.nspname = 'schema_name'
          AND   c.relname = 'table_name'
          AND   c.relkind = 'r'     -- only tables
    )) THEN     
       INSERT INTO listings_changes
         SELECT now(), 'DELETE', OLD.*;
       RETURN OLD;
       ELSE RAISE EXCEPTION 'Table does not exists';
     END IF; 
    ELSIF (TG_OP = 'UPDATE') THEN
      IF (EXISTS (
          SELECT 1
          FROM pg_catalog.pg_class c
          JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
          WHERE n.nspname = 'schema_name'
          AND   c.relname = 'table_name'
          AND   c.relkind = 'r'     -- only tables
    )) THEN     
       INSERT INTO listings_changes
         SELECT now(), 'UPDATE', NEW.*;
       RETURN NEW;
       ELSE RAISE EXCEPTION 'Table does not exists';
     END IF;            
    ELSEIF (TG_OP = 'INSERT') THEN
     
       INSERT INTO listings_changes
         SELECT now(), 'INSERT', NEW.*;
       RETURN NEW;
      
    END IF;
    EXCEPTION
    WHEN SQLSTATE '42611' THEN
      RAISE EXCEPTION 'Columns do not match audit file does not match user file';
    WHEN SQLSTATE '42P16' THEN
      RAISE EXCEPTION 'Table does not exists';
    WHEN OTHERS THEN  
      RAISE EXCEPTION 'PostgresSQL error code that has occurred';
    RETURN SQLSTATE; 
    END;
$listings_audit$ LANGUAGE plpgsql;