I am trying to migrate data from one table to another in postgresql via record but it throws error when null values in insert statement

ERROR:  syntax error at or near "," LINE 1: ...s Promo",,<ht...                                                                                                                      
QUERY:  insert into site_target values (100001,"2024-07-10 17:45:16.785991+00","2024-07-10 17:45:16.786007+00",100001,,1,1,0,"Monday to Friday 10AM-6PM",,0,0,0,0,0,,,0,,,,) CONTEXT:  PL/pgSQL function data_movement_ref4(character varying,character varying,timestamp without time zone,timestamp without time zone) line 29 at EXECUTE SQL state: 42601

    create or replace procedure data_movement_ref4(source_table  in varchar, target_table in varchar, p_minimum_date in timestamp, p_end_date in timestamp ) 
    language plpgsql 
    as $$ 
    declare lv_string character varying(3000);
    v_sql character varying(3000); 
    loop_rec record; rec1 record; 
    cnt int; 
    c_cursor refcursor;
    p_min_dt timestamp;
    p_end_dt timestamp;
    begin
    
    raise notice '%',p_minimum_date ;
    v_sql:='insert into '||target_table||' values ';
    open c_cursor for execute 'select * from '||source_table|| ';'; 
             loop
               fetch c_cursor into loop_rec;
               exit when not found;
               execute v_sql|| loop_rec;
               raise notice '%',loop_rec ;
               cnt := cnt+1;
                    if cnt = 10000 then
                    commit;
                    end if;
                 end loop;
    close c_cursor;
    end; 
    $$