Fix link param

htdocs/contrat/list.php

@@ -421,16 +421,16 @@ if ($search_dfyear != '') {
 if ($search_dfmonth != '') {
 	$param .= '&search_dfmonth='.urlencode($search_dfmonth);
 }
-if ($search_sale != '') {
+if ($search_sale > 0) {
 	$param .= '&search_sale='.urlencode($search_sale);
 }
-if ($search_user != '') {
+if ($search_user > 0) {
 	$param .= '&search_user='.urlencode($search_user);
 }
-if ($search_type_thirdparty != '' && $search_type_thirdparty > 0) {
+if ($search_type_thirdparty > 0) {
 	$param .= '&search_type_thirdparty='.urlencode($search_type_thirdparty);
 }
-if ($search_product_category != '') {
+if ($search_product_category > 0) {
 	$param .= '&search_product_category='.urlencode($search_product_category);
 }
 if ($show_files) {