#vulnerable code 
                                @Test
    public void testConfig() {
        final LoggerContext ctx = Configurator.initialize("Test1", "target/test-classes/log4j2-sdfilter.xml");
        final Configuration config = ctx.getConfiguration();
        final Filter filter = config.getFilter();
        assertNotNull("No StructuredDataFilter", filter);
        assertTrue("Not a StructuredDataFilter", filter instanceof  StructuredDataFilter);
        final StructuredDataFilter sdFilter = (StructuredDataFilter) filter;
        assertFalse("Should not be And filter", sdFilter.isAnd());
        final Map<String, List<String>> map = sdFilter.getMap();
        assertNotNull("No Map", map);
        assertFalse("No elements in Map", map.isEmpty());
        assertEquals("Incorrect number of elements in Map", 1, map.size());
        assertTrue("Map does not contain key eventId", map.containsKey("eventId"));
        assertEquals("List does not contain 2 elements", 2, map.get("eventId").size());
    } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testConfig() {
        final Configuration config = context.getConfiguration();
        final Filter filter = config.getFilter();
        assertNotNull("No StructuredDataFilter", filter);
        assertTrue("Not a StructuredDataFilter", filter instanceof  StructuredDataFilter);
        final StructuredDataFilter sdFilter = (StructuredDataFilter) filter;
        assertFalse("Should not be And filter", sdFilter.isAnd());
        final Map<String, List<String>> map = sdFilter.getMap();
        assertNotNull("No Map", map);
        assertFalse("No elements in Map", map.isEmpty());
        assertEquals("Incorrect number of elements in Map", 1, map.size());
        assertTrue("Map does not contain key eventId", map.containsKey("eventId"));
        assertEquals("List does not contain 2 elements", 2, map.get("eventId").size());
    }