BUGFIX: scanning.php COUPONTAX

At line 131 this was testing for an integer. SELECT of valeu="0" always failed.
129 if (isset($_REQUEST['COUPONTAX'])) 
      $CORE_LOCAL->set('CouponsAreTaxable',$_REQUEST['COUPONTAX']);
130 echo '<select name="COUPONTAX">';
131 if ($CORE_LOCAL->get('CouponsAreTaxable') === '0')