I stumbled across this error (see attached PNG) when showing the PHP notice errors:

SYSTEM NOTICE: Use of undefined constant NONE - assumed 'NONE'

1. The cause of this is because the file "constants_inc.php" is missing a constant in the "directions" area called NONE.
   Code:
   define( 'NONE', 103 );
   
2. In the "icon_api.php" file add NONE and the image to the array for variable $g_sort_icon_array.
   Code:

   Sort direction to icon mapping

       $g_sort_icon_arr = array (
               ASC        => 'up.gif',
               DESC       => 'down.gif',
               NONE      => 'blank.gif'
       );

I hope this helps. No one will notice this error with the option $g_show_notices turned OFF. But better to fix it then not.