FIX #5128 if create method return duplicated code error

not use GETPOST in order to get a new code

htdocs/langs/en_US/companies.lang

@@ -432,3 +432,4 @@ MergeThirdparties=Merge third parties
 ConfirmMergeThirdparties=Are you sure you want to merge this third party into the current one ? All linked objects (invoices, orders, ...) will be moved to current third party so you will be able to delete the duplicate one.
 ThirdpartiesMergeSuccess=Thirdparties have been merged
 ErrorThirdpartiesMerge=There was an error when deleting the thirdparties. Please check the log. Changes have been reverted.
+NewCustomerSupplierCodeProposed=New customer or supplier proposed on duplicate code

htdocs/societe/soc.php

@@ -505,6 +505,13 @@ if (empty($reshook))
                 }
                 else
 				{
+					
+					if($result == -3) {
+						$duplicate_code_error = true;
+						$object->code_fournisseur = null;
+						$object->code_client = null;
+					}
+					
                     $error=$object->error; $errors=$object->errors;
                 }
 
@@ -794,8 +801,14 @@ else
         $object->particulier		= $private;
         $object->prefix_comm		= GETPOST('prefix_comm');
         $object->client				= GETPOST('client')?GETPOST('client'):$object->client;
+        
+        if(empty($duplicate_code_error)) {
 	        $object->code_client		= GETPOST('code_client', 'alpha');
 	        $object->fournisseur		= GETPOST('fournisseur')?GETPOST('fournisseur'):$object->fournisseur;
+        }
		else {
+			setEventMessages($langs->trans('NewCustomerSupplierCodeProposed'),'', 'warnings');
+		}
+		
         $object->code_fournisseur	= GETPOST('code_fournisseur', 'alpha');
         $object->address			= GETPOST('address', 'alpha');
         $object->zip				= GETPOST('zipcode', 'alpha');