Error in OVS!!

Question

i am getting error which is mentioned below regarding OVS,particularly when the browser is running slow and i am clicking 2nd time for the value help.
If anyone know the answer,give me the solution.
I will reward point.
error is like ....
The following error text was processed in the system EC6 : Access via 'NULL' object reference not possible.
The error occurred on the application server HSDNT24S12_EC6_03 and in the work process 0 .
The termination type was: RABAX_STATE
The ABAP call stack was:
Method: IF_WDR_OVS_LISTENER~MODIFY_RESULT_VIEW of program CL_WDR_VALUE_HELP_HANDLER=====CP
Method: WDDOMODIFYVIEW of program /1BCWDY/RZ2TAVAGXRRTKWWIR62K==CP
Method: IF_WDR_VIEW_DELEGATE~WD_DO_MODIFY_VIEW of program /1BCWDY/RZ2TAVAGXRRTKWWIR62K==CP
Method: DO_MODIFY_VIEW of program CL_WDR_DELEGATING_VIEW========CP
Method: MODIFY_VIEW of program CL_WDR_VIEW===================CP
Method: DO_MODIFY_VIEW of program CL_WDR_CLIENT_COMPONENT=======CP
Method: DO_MODIFY_VIEW of program CL_WDR_WINDOW_PHASE_MODEL=====CP
Method: PROCESS_REQUEST of program CL_WDR_WINDOW_PHASE_MODEL=====CP
Method: PROCESS_REQUEST of program CL_WDR_WINDOW=================CP
Method: EXECUTE of program CL_WDR_MAIN_TASK==============CP
thanks in advance,
Subhasis.

Answer 1

HI,
DID U WRITE THE FOLLOWING CODE IN A METHOD :
  types : begin of ist_fields,
           carrid type spfli-carrid,
           countryfr type spfli-countryfr,
           cityfrom type spfli-cityfrom,
         end of ist_fields.
  data:
        it_fields type ist_fields,
        it_conn   type table of spfli.
  field-symbols : <lfs_input> type ist_fields,
                  <lfs_select> type spfli.
  case ovs_callback_object->phase_indicator.
    when 0.
      call method ovs_callback_object->set_configuration
        exporting
          window_title       = 'search Flights'
          group_header       = 'enter flight details'
         LABEL_TEXTS        =
         TABLE_HEADER       =
         COLUMN_TEXTS       =
          col_count          = 1
         ROW_COUNT          =
         TABLE_MULTI_SELECT =
    when 1.
      call method ovs_callback_object->set_input_structure
        exporting
          input        = it_fields
           GROUP_HEADER =
           LABEL_TEXTS  =
           WINDOW_TITLE =
    when 2.
      assign ovs_callback_object->query_parameters->* to <lfs_input> casting.
       call method cl_wd_flight_model=>get_conns_by_carrid_cityfrom
         exporting
           i_carrid         = <lfs_input>-carrid
           i_countryfr      = <lfs_input>-countryfr
           i_cityfrom       = <lfs_input>-cityfrom
         importing
          et_spfli_sflight = it_conn
       call method ovs_callback_object->set_output_table
         exporting
           output       =  it_conn
          TABLE_HEADER =
          COLUMN_TEXTS =
     when 3.
         data:
           node_flight                         type ref to if_wd_context_node,
           elem_flight                         type ref to if_wd_context_element,
           stru_flight                         type if_inputview=>element_flight .
         assign ovs_callback_object->selection->* to <lfs_select> casting.
       navigate from <CONTEXT> to <FLIGHT> via lead selection
         node_flight = wd_context->get_child_node( name = if_inputview=>wdctx_flight ).
        node_flight->bind_structure(
          exporting
            new_item             = <lfs_select> ).
AND ALSO IN THE CONTEXT DID U SELECT OBJECT VALUE SELECTOR IN INPUT HELP MODE3 AND OVS COMPONENT USAGE.
MADHU