testTriple: Object test used getSubject, should be getObject

This causes an exception in addWhere:
```
    public static void main(String[] args) {
        Node s = SSE.parseNode("
") ;
        Node p = SSE.parseNode("<p>") ;
        Node v = SSE.parseNode("?v") ;
        Node o = SSE.parseNode("<o>") ;
        
        SelectBuilder qb = new SelectBuilder() ;
        qb.getWhereHandler().addWhere(Triple.create(s, p, v)) ;
        Query q = qb.build() ;
        System.out.println(q) ;
    }
```