#vulnerable code 
                                @Test
    public void testFieldPopulator()
    {
        Album funeral = DataGenerator.funeral();
        ResultTraverser traverser = new ResultTraverser();
        populatorRegistry.register( new AlbumFieldPopulator() );

        YogaRequestContext requestContext = new YogaRequestContext( "test",
                new DummyHttpServletRequest(), new DummyHttpServletResponse(), new HrefListener( this.populatorRegistry ) );
        Map<String, Object> objectTree = doTraverse( funeral, ":", traverser, requestContext );

        Assert.assertEquals( "/album/" + funeral.getId() + ".test", objectTree.get( "href" ) );
    } 
                            #location 12 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testFieldPopulator()
    {
        Album funeral = DataGenerator.funeral();
        ResultTraverser traverser = new ResultTraverser();
        populatorRegistry.register( new AlbumFieldPopulator() );

        YogaRequestContext requestContext = new YogaRequestContext( "test", new GDataSelectorParser(),
                new DummyHttpServletRequest(), new DummyHttpServletResponse(), new HrefListener( this.populatorRegistry ) );
        Map<String, Object> objectTree = doTraverse( funeral, ":", traverser, requestContext );

        Assert.assertEquals( "/album/" + funeral.getId() + ".test", objectTree.get( "href" ) );
    }