Add already exists check

Add check to pbo module to check if tree already exists, so it does not try and create it again!


*--------------------------------------------------------------*
***INCLUDE ZDEMO_ALVTREEO01 .
*--------------------------------------------------------------*
*&-------------------------------------------------------------*
*&      Module  STATUS_0100  OUTPUT
*&-------------------------------------------------------------*
*       text
*--------------------------------------------------------------*
MODULE status_0100 OUTPUT.
  SET PF-STATUS 'STATUS1'.
*  SET TITLEBAR 'xxx'.

* If ALVtree already exists then it  mush not be re-created as this
* will cause a runtime error.
  IF gd_tree IS INITIAL.
*   Create ALVtree (must be performed within screen PBO module)
    PERFORM create_alvtree_container.
    PERFORM create_object_in_container.
    perform define_events.
    PERFORM create_alvtree_hierarchy.
  ENDIF.
  CALL METHOD cl_gui_cfw=>flush.

ENDMODULE.                 " STATUS_0100  OUTPUT

Add already exists check!