APEX

when use plugin for workflow

function complete_tasks ( 
   p_process in apex_plugin.t_process,
   p_plugin  in apex_plugin.t_plugin,
   p_param   in apex_plugin.t_process_complete_param )
   return apex_plugin.t_process_complete_result
is 
   l_result            apex_plugin.t_process_complete_result;
begin
   l_result.status     := apex_plugin.c_complete_status_success;
   return l_result;
end;
function create_tasks (
   p_process in apex_plugin.t_process,
   p_plugin  in apex_plugin.t_plugin )
   return apex_plugin.t_process_exec_result
is
   
   c_workflowid        constant varchar2(32767) := p_process.attribute_01;
   l_api_params        apex_approval.t_task_parameters;
   l_index             pls_integer := 0;
   l_task_id           number;
   l_workflowid        number;
   l_addby  number;
   l_result            apex_plugin.t_process_exec_result;
begin
   l_workflowid   := to_number(v(c_workflowid));
   BEGIN
       SELECT saddby
           INTO l_addby
       FROM employee
       WHERE SC_WORKFLOWID = l_workflowid;
   END;
       l_task_id := apex_approval.create_task(
           p_application_id => :APP_ID,
           p_task_def_static_id => 'test_id_1',
           p_initiator => l_sc_addby,
           p_parameters => apex_approval.t_task_parameters(
              1 => apex_approval.t_task_parameter(static_id => 'WORKFLOWID',  string_value => l_workflowid)
       ),
           p_detail_pk => l_workflowid           
   );
   return l_result;
end;

SELECT * FROM APEX_TASKS
why column WORKFLOW_ID IS NULL