Getting a program Dump Error in Herarchial ALV

Question

Hello All,
I am getting a dump error when I am executing the below program. Kindly help as I am not getting the output. However all the subroutines are getting properly populated with data. Getting a dump error while calling the function : REUSE_ALV_HIERSEQ_LIST_DISPLAY
Pasted below are both the question and solution. Copy the solution in SE38 and execute it to check out the dump error.
Kindly help.
Thanks,
Vinod.
QUESTION :-
Objective
     Hierarchical ALV for displaying Sales documents per customer
Design
     Create a program that will allow the user to display all customers that have placed Sales Orders in the given date range. The user will have an ability to drill-down to see the sales order items per customer.
     Selection screen fields–
          Sales order creation date (range)
          Customer number (range)
     Output –
          Header –
               Customer Number
               Customer Name
               Total Order value (sum of order values from items below)
          Details –
Sales order number
Material number
Order quantity
Order value
Reference
     Tables:  KNA1, VBAK, VBAP
     Transaction – VA03 (Sales order)
SOLUTION :-
*& Report  Z_HALV_32722                                                *
REPORT  Z_HALV_32722                            .
TYPE-POOLS: slis.
TABLES : kna1,
         vbak.
SELECT-OPTIONS: s_cst_no FOR kna1-kunnr.
SELECT-OPTIONS: s_cr_dt FOR vbak-erdat.
DATA : BEGIN of ty_hdr,
        kunnr TYPE vbak-kunnr,
        name1 TYPE kna1-name1,
        netwr TYPE vbak-netwr,
        END of ty_hdr,
        gt_hdr LIKE TABLE OF ty_hdr,
        gs_hdr LIKE LINE OF gt_hdr.
DATA : BEGIN of ty_ln,
        kunnr TYPE vbak-kunnr,
        vbeln TYPE vbap-vbeln,
        matnr TYPE vbap-matnr,
        kwmeng TYPE vbap-kwmeng,
        netwr TYPE vbap-netwr,
        END of ty_ln,
        gt_ln LIKE TABLE OF ty_ln,
        gs_ln LIKE LINE OF gt_ln.
DATA : BEGIN of ty_hdr1,
        kunnr TYPE vbak-kunnr,
        END of ty_hdr1,
        gt_hdr1 LIKE TABLE OF ty_hdr1,
        gs_hdr1 LIKE LINE OF gt_hdr1.
DATA : gt_fc TYPE slis_t_fieldcat_alv,
       gs_fc LIKE LINE OF gt_fc,
       gs_k_fld TYPE  slis_keyinfo_alv,
       gt_layout TYPE slis_layout_alv,
       gv_repid  TYPE sy-repid.
START-OF-SELECTION.
gv_repid = sy-repid.
perform fetch_data.
perform prepare_fc.
perform prepare_layout.
perform show_output.
*&      Form  fetch_data
      text
-->  p1        text
<--  p2        text
form fetch_data .
SELECT kunnr
INTO CORRESPONDING FIELDS OF TABLE gt_hdr1
FROM vbak
WHERE vbak~kunnr IN s_cst_no
AND vbak~erdat IN s_cr_dt.
DELETE ADJACENT DUPLICATES FROM gt_hdr1 COMPARING kunnr.
LOOP AT gt_hdr1 INTO gs_hdr1.
  SELECT SINGLE vbakkunnr kna1name1 SUM( vbak~netwr )
  INTO (gs_hdr-kunnr, gs_hdr-name1, gs_hdr-netwr)
  FROM vbak INNER JOIN kna1
  ON vbakkunnr = kna1kunnr
  WHERE vbak~kunnr = gs_hdr1-kunnr
  GROUP BY vbakkunnr kna1name1.
  APPEND gs_hdr TO gt_hdr.
  SELECT vbakkunnr vbapvbeln vbapmatnr vbapkwmeng vbap~netwr
  INTO CORRESPONDING FIELDS OF TABLE gt_ln
  FROM vbap INNER JOIN vbak
  ON vbapvbeln = vbakvbeln
  WHERE vbak~kunnr = gs_hdr1-kunnr.
ENDLOOP.
endform.                    " fetch_data
*&      Form  prepare_fc
      text
-->  p1        text
<--  p2        text
form prepare_fc .
  CLEAR gs_k_fld.
  gs_k_fld-header01 = 'KUNNR'.
  gs_k_fld-item01   = 'KUNNR'.
  CLEAR gs_fc.
  gs_fc-fieldname = 'KUNNR'.
  gs_fc-tabname   = 'GT_HDR'.
  gs_fc-seltext_l = text-001.
  APPEND gs_fc TO gt_fc.
  CLEAR gs_fc.
  gs_fc-fieldname = 'NAME1'.
  gs_fc-tabname   = 'GT_HDR'.
  gs_fc-seltext_l = text-002.
  APPEND gs_fc TO gt_fc.
  CLEAR gs_fc.
  gs_fc-fieldname = 'NETWR'.
  gs_fc-tabname   = 'GT_HDR'.
  gs_fc-seltext_l = text-003.
  APPEND gs_fc TO gt_fc.
  CLEAR gs_fc.
  gs_fc-fieldname = 'VBELN'.
  gs_fc-tabname   = 'GT_LN'.
  gs_fc-seltext_l = text-004.
  APPEND gs_fc TO gt_fc.
  CLEAR gs_fc.
  gs_fc-fieldname = 'MATNR'.
  gs_fc-tabname   = 'GT_LN'.
  gs_fc-seltext_l = text-005.
  APPEND gs_fc TO gt_fc.
  CLEAR gs_fc.
  gs_fc-fieldname = 'KWMENG'.
  gs_fc-tabname   = 'GT_LN'.
  gs_fc-seltext_l = text-006.
  APPEND gs_fc TO gt_fc.
  CLEAR gs_fc.
  gs_fc-fieldname = 'NETWR'.
  gs_fc-tabname   = 'GT_LN'.
  gs_fc-seltext_l = text-007.
  APPEND gs_fc TO gt_fc.
endform.                    " prepare_fc
*&      Form  prepare_layout
      text
-->  p1        text
<--  p2        text
form prepare_layout .
gt_layout-colwidth_optimize = 'X'.
gt_layout-expand_fieldname = 'TST'.
endform.                    " prepare_layout
*&      Form  show_output
      text
-->  p1        text
<--  p2        text
form show_output .
CALL FUNCTION 'REUSE_ALV_HIERSEQ_LIST_DISPLAY'
  EXPORTING
  I_INTERFACE_CHECK              = ' '
    I_CALLBACK_PROGRAM             = gv_repid
  I_CALLBACK_PF_STATUS_SET       = ' '
  I_CALLBACK_USER_COMMAND        = ' '
    IS_LAYOUT                      = gt_layout
    IT_FIELDCAT                    = gt_fc
  IT_EXCLUDING                   =
  IT_SPECIAL_GROUPS              =
  IT_SORT                        =
  IT_FILTER                      =
  IS_SEL_HIDE                    =
  I_SCREEN_START_COLUMN          = 0
  I_SCREEN_START_LINE            = 0
  I_SCREEN_END_COLUMN            = 0
  I_SCREEN_END_LINE              = 0
  I_DEFAULT                      = 'X'
  I_SAVE                         = ' '
  IS_VARIANT                     =
  IT_EVENTS                      =
  IT_EVENT_EXIT                  =
    i_tabname_header               = 'GT_HDR'
    i_tabname_item                 = 'GT_LN'
  I_STRUCTURE_NAME_HEADER        =
  I_STRUCTURE_NAME_ITEM          =
    is_keyinfo                     = gs_k_fld
  IS_PRINT                       =
  IS_REPREP_ID                   =
  I_BYPASSING_BUFFER             =
  I_BUFFER_ACTIVE                =
IMPORTING
  E_EXIT_CAUSED_BY_CALLER        =
  ES_EXIT_CAUSED_BY_USER         =
  tables
    t_outtab_header                = GT_HDR[]
    t_outtab_item                  = GT_LN[]
EXCEPTIONS
  PROGRAM_ERROR                  = 1
  OTHERS                         = 2
IF sy-subrc <> 0.
MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
        WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
ENDIF.
endform.                    " show_output

Answer 1

Everything looks fine with the gt_layout, it is not an internal table, so no need to append to it, it is simply a structure, but you do tell it that TST is the expand field, but there is no field of this name in your internal for the header, so add it like this.
DATA : BEGIN of ty_hdr,
kunnr TYPE vbak-kunnr,
name1 TYPE kna1-name1,
netwr TYPE vbak-netwr,
<b>TST  type c,</b>
END of ty_hdr,
Doing so should make you program work correctly.
Regards,
Rich Heilman
Message was edited by:
        Rich Heilman