Solution
I find the solution of my problem
if someone needs it i have modify
\include\class.ticket.php function close ()
function close(){
if('$staff_id' > 0) {
// $sql= 'UPDATE '.TICKET_TABLE.' SET status='.db_input('closed').',staff_id=0,isoverdue=0,duedate=NULL,updated=NOW(),closed=NOW() '.
$sql= 'UPDATE '.TICKET_TABLE.' SET status='.db_input('closed').',isoverdue=0,duedate=NULL,updated=NOW(),closed=NOW() '.
' WHERE ticket_id='.db_input($this->getId());
} else {
global $thisuser;
$sql= 'UPDATE '.TICKET_TABLE.' SET status='.db_input('closed').',<STRONG><s>**</s>staff_id='.db_input($thisuser->getId()).<e>**</e></STRONG>',isoverdue=0,duedate=NULL,updated=NOW(),closed=NOW() '.
' WHERE ticket_id='.db_input($this->getId());
}
return (db_query($sql) && db_affected_rows())?true;
}