no border in cl_gui_docking_container

Hi. I have a progrm:

DATA:
docking TYPE REF TO cl_gui_docking_container,
picture_control_1 TYPE REF TO cl_gui_picture,
url(256) TYPE c .

PARAMETERS: p_dummy TYPE c .

AT SELECTION-SCREEN OUTPUT.
PERFORM show_pic.

START-OF-SELECTION.


*&---------------------------------------------------------------------*
*& Form show_pic
*&---------------------------------------------------------------------*
FORM show_pic.

DATA: repid LIKE sy-repid.
DATA: file_name LIKE sapb-sapfiles,
file_type LIKE bdn_con-mimetype.

repid = sy-repid.
IF docking IS INITIAL .
CREATE OBJECT docking
EXPORTING
repid = repid
dynnr = sy-dynnr
side = cl_gui_docking_container=>dock_at_right
extension = '200'
EXCEPTIONS
cntl_error = 1
cntl_system_error = 2
create_error = 3
lifetime_error = 4
lifetime_dynpro_dynpro_link = 5.



CREATE OBJECT picture_control_1 EXPORTING parent = docking.

CHECK sy-subrc = 0.



CALL FUNCTION 'DP_PUBLISH_WWW_URL'
EXPORTING
objid = 'HTMLCNTL_TESTHTM2_SAP_AG'
lifetime = 'T'
IMPORTING
url = url
EXCEPTIONS
OTHERS = 1.

* Load the picture by using the url generated by the data provider.
IF sy-subrc = 0.
CALL METHOD picture_control_1->load_picture_from_url_async
EXPORTING
url = url.
ENDIF.
ENDIF .

ENDFORM. "show_pic

The docking container appears with border. Could You tell me how to remove that border? Greetings. P.