cl_gui_alv_grid get_selected_rows return empty lvc_t_row

Hi,

DATA : rows TYPE lvc_t_row,

            wa_row TYPE lvc_s_row.

   gs_layout-sel_mode   = 'A'.

   gs_layout-box_fname = 'SEL'.

   gs_layout-cwidth_opt = 'X'.

   gs_layout-zebra      = 'X'.

   gs_variant-report    = sy-repid.

CALL METHOD g_grid->get_selected_rows

   IMPORTING

     et_index_rows = rows

*    et_row_no     =

     .

IF rows[] is INITIAL.

MESSAGE 'Satır seçiniz!' TYPE 'S'.

EXIT.

ENDIF.

LOOP AT rows INTO wa_row.

delete gt_out INDEX wa_row-index.

ENDLOOP.

why rows return empty?

Thanks.

Ömer