How to solve when progress indicator show up when closing a form in Oracle Apps Custom Form in EBS

I have misunderstood the '<your first window>' in
APP_CUSTOM (Package Body).

I set it like this '<window_name>'

Correct it  remove the brackets like 'window_name' example : 'WINDOW_MAIN'

 if (wnd = 'WINDOW_MAIN') then
    app_window.close_first_window;
  elsif (wnd = '<another window>') then
    --defer relations
    --close related windows  
    null; 
  elsif (wnd = '<yet another window>') then
    --defer relations
    --close related windows  
    null;
  end if;