Access via 'NULL' object reference not possible

Hi,

I know that there is so many questions about this error message but i can't solve my problem yet.

My node 'cevaplar' has this properties : cardinality : 0..n and selection : 0..1 and this is the code which is displayed in ST22. please help.

2177
2178 IF sy-subrc ne 0.
2179     lv_hata = 'Bu soruya verilmiu015F bir yanu0131t bulunmamaktadu0131r!'.
2180
2181 else.
>>>>
2183  lo_nd_cevaplar->bind_elements( lt_cevaplar ).
2184
2185
2186 l_cmp_api        = wd_comp_controller->wd_get_api( ).
2187 l_window_manager = l_cmp_api->get_window_manager( ).
2188 wd_comp_controller->popup = l_window_manager->create_window(
2189            window_name = 'CEVAPGOSTER'
2190            close_button = abap_true ).
2191 wd_comp_controller->popup->open(  ).
2192
2193 endif.