'OBJECTS_OBJREF_NOT_ASSIGNED_NO' Runtime Error in abap program

Question

When my dubugger goes on this line..it gives me Runtime error'
'OBJECTS_OBJREF_NOT_ASSIGNED_NO'
CX_SY_REF_IS_INITIAL
Code :
CALL METHOD determine_budget_values->determine_budget_values
  EXPORTING
     plvar  = '.:'
     butyp  = 'BU'
     begda  = '20060101'  "'01.01.2006'
     endda  = '20061231'  "'31.12.2006'
     kcurr  = 'X'
     budot  = 'BU'
     budid  = '50012433'  "objektid
     oldam  = 1000
     oldcu  = 'USD'
     oldno  = 10
     oldsu  = 'USD'
  IMPORTING
    NEWAM  = newam
    NEWCU  = newcu.
  NEWNO  =
  NEWSU  =
Thanx in advance....Its very urgent..

Answer 1

Thanks a lott...for u r rhelp///
but one thing i would like to know after executing properly this method....will my HRP1520 will get those new values of budget of i will have to code it in Method ..specifically.
i m sending code for Method...
method IF_EX_HRECM00_BDG0001~DETERMINE_BUDGET_VALUES.
  DATA: BEGIN OF fs_budgets               ,
          objid(8) TYPE n                 ,             " Object Id
          flag     TYPE c                 ,             " Monetary/Non Monetary
          newam    TYPE CHAR22            ,             " Budgeted Amount,
          newcu    TYPE CHAR05            ,             " Currency Key,
        END OF fs_budgets                 ,
        t_budgets LIKE TABLE OF fs_budgets.
  DATA: w_sobid   TYPE hrp1001-sobid      ,             " Org. Unit
        w_file    TYPE rlgrap-filename    .             " File Name
  DATA: t_orgunit      TYPE hap_t_hrsobid    ,          " Id of Org. unit
        t_suborgunits  TYPE hap_t_hrsobid    ,          " Ids of Sub Org Units
        fs_orgunit     LIKE LINE OF t_orgunit.          " Work Area of orgunit
  REFRESH: t_orgunit,
           t_suborgunits.
  CLEAR  : fs_orgunit..
The Budget values are stored in the file 'BUDGETS' on the App Server*
This data will be read from the App Server                          *
  w_file = 'BUDGETS'.
  OPEN DATASET w_file FOR INPUT IN TEXT MODE ENCODING DEFAULT.
Fetching the corresponding Org Unit for the Budget Id               *
  SELECT sobid                         " Org. Unit
    FROM hrp1001
    INTO w_sobid
   WHERE plvar EQ '01'
     AND otype EQ 'BU'
     AND objid EQ  budid
     AND rsign EQ 'B'
     AND relat EQ '300'
     AND istat EQ '1'
     AND begda LE  endda
     AND endda GE  begda.
  ENDSELECT.                           " SELECT sobid
  IF sy-subrc EQ 0.
    fs_orgunit-plvar = '01'.
    fs_orgunit-otype = 'O'.
    fs_orgunit-sobid = w_sobid.
    APPEND fs_orgunit TO t_orgunit.
    CLEAR  fs_orgunit.
Fetching the Sub Org units for a given Org unit                     *
    CALL FUNCTION 'HRHAP_SEL_OBJECTS_OF_EVAL_PATH'
      EXPORTING
        T_OBJECTS_BASE   =  t_orgunit
        EVALUATION_PATH  = 'ORGEH'
        FROM_DATE        =  begda
        TO_DATE          =  endda
      IMPORTING
        T_OBJECTS        =  t_suborgunits.
  ENDIF.                               " IF sy-subrc EQ 0.
  CLEAR newam.
Accumulating the budget values of all the Sub org units for a given *
Org unit and populating the fields 'newam' and 'newcu'.             *
  LOOP AT t_suborgunits INTO fs_orgunit.
    CLOSE DATASET w_file.
    OPEN DATASET w_file FOR INPUT IN TEXT MODE ENCODING DEFAULT.
    DO.
      READ DATASET w_file INTO fs_budgets.
      IF sy-subrc EQ 0.
        IF fs_budgets-objid EQ fs_orgunit-sobid.
          ADD fs_budgets-newam TO newam.
          newcu = fs_budgets-newcu.
          EXIT.
        ENDIF.
      ELSE.
        EXIT.
      ENDIF.                           " IF sy-subrc EQ 0.
    ENDDO.                             " DO
  ENDLOOP.                             " LOOP AT t_suborgunits
Giving default values for the Budget Amount and Currency if they are*
containing Initial values                                           *
  IF newam IS INITIAL.
    newam = 0.
  ENDIF.                               " IF newam IS INITIAL.
  IF newcu IS INITIAL.
    newcu = 'USD'.
  ENDIF.                               " IF newcu IS INITIAL.
  CLOSE DATASET w_file.
endmethod.
After this code will i require to code anything specific to get this newam(new amount) uploaded to HRP1520 infotype or automatically it will upload if i write above mentioned code only...
Please revert......thanx  a lot