#vulnerable code 
                                @Test
    public void testEnvironment() throws Exception {
        ctx = Configurator.initialize("-config", null);
        LogManager.getLogger("org.apache.test.TestConfigurator");
        final Configuration config = ctx.getConfiguration();
        assertNotNull("No configuration", config);
        assertEquals("Incorrect Configuration.", CONFIG_NAME, config.getName());
        final Map<String, Appender> map = config.getAppenders();
        assertNotNull("Appenders map should not be null.", map);
        assertTrue("Appenders map should not be empty.", map.size() > 0);
        Appender app = null;
        for (final Map.Entry<String, Appender> entry: map.entrySet()) {
            if (entry.getKey().equals("List2")) {
                app = entry.getValue();
                break;
            }
        }
        assertNotNull("No ListAppender named List2", app);
        final Layout<? extends Serializable> layout = app.getLayout();
        assertNotNull("Appender List2 does not have a Layout", layout);
        assertTrue("Appender List2 is not configured with a PatternLayout", layout instanceof PatternLayout);
        final String pattern = ((PatternLayout) layout).getConversionPattern();
        assertNotNull("No conversion pattern for List2 PatternLayout", pattern);
        assertFalse("Environment variable was not substituted", pattern.startsWith("${env:PATH}"));
    } 
                            #location 19 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testEnvironment() throws Exception {
        ctx = Configurator.initialize("-config", null);
        LogManager.getLogger("org.apache.test.TestConfigurator");
        final Configuration config = ctx.getConfiguration();
        assertNotNull("No configuration", config);
        assertEquals("Incorrect Configuration.", CONFIG_NAME, config.getName());
        final Map<String, Appender> map = config.getAppenders();
        assertNotNull("Appenders map should not be null.", map);
        assertThat(map, hasSize(greaterThan(0)));
        assertThat("No ListAppender named List2", map, hasKey("List2"));
        Appender app = map.get("List2");
        final Layout<? extends Serializable> layout = app.getLayout();
        assertNotNull("Appender List2 does not have a Layout", layout);
        assertThat("Appender List2 is not configured with a PatternLayout", layout, instanceOf(PatternLayout.class));
        final String pattern = ((PatternLayout) layout).getConversionPattern();
        assertNotNull("No conversion pattern for List2 PatternLayout", pattern);
        assertFalse("Environment variable was not substituted", pattern.startsWith("${env:PATH}"));
    }