rank duplicate on mass action

#### rank duplicate on mass action  invoice from multiple orders

we have to  define the max rank for each line which makes it possible not to have a duplicate on the rank field in the case of several order massaction request.

htdocs/core/actions_massactions.inc.php

@@ -791,7 +791,10 @@ if ($massaction == 'confirm_createbills') {   // Create bills from orders.
 							'HT',
 							0,
 							$product_type,
-							$lines[$i]->rang,
+							
+							//we have define the max rank for each line which makes it possible not to have a duplicate on the rank field in the case of several orders
+							//-1 will give us the right number
+							-1, // rank
 							$lines[$i]->special_code,
 							$objecttmp->origin,
 							$lines[$i]->rowid,