#vulnerable code 
                                private void compareLogEvents(final LogEvent orig, final LogEvent changed) {
        // Ensure that everything but the Mapped Data is still the same
        Assert.assertEquals("LoggerName changed", orig.getLoggerName(), changed.getLoggerName());
        Assert.assertEquals("Marker changed", orig.getMarker(), changed.getMarker());
        Assert.assertEquals("FQCN changed", orig.getLoggerFqcn(), changed.getLoggerFqcn());
        Assert.assertEquals("Level changed", orig.getLevel(), changed.getLevel());
        Assert.assertArrayEquals("Throwable changed", orig.getThrown() == null //
                ? null //
                : ((Log4jLogEvent) orig).getThrownProxy().getExtendedStackTrace(), //
                changed.getThrown() == null //
                        ? null //
                        : ((Log4jLogEvent) changed).getThrownProxy().getExtendedStackTrace());
        Assert.assertEquals("ContextMap changed", orig.getContextMap(), changed.getContextMap());
        Assert.assertEquals("ContextStack changed", orig.getContextStack(), changed.getContextStack());
        Assert.assertEquals("ThreadName changed", orig.getThreadName(), changed.getThreadName());
        Assert.assertEquals("Source changed", orig.getSource(), changed.getSource());
        Assert.assertEquals("Millis changed", orig.getTimeMillis(), changed.getTimeMillis());
    } 
                            #location 9 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                private void compareLogEvents(final LogEvent orig, final LogEvent changed) {
        // Ensure that everything but the Mapped Data is still the same
        assertEquals("LoggerName changed", orig.getLoggerName(), changed.getLoggerName());
        assertEquals("Marker changed", orig.getMarker(), changed.getMarker());
        assertEquals("FQCN changed", orig.getLoggerFqcn(), changed.getLoggerFqcn());
        assertEquals("Level changed", orig.getLevel(), changed.getLevel());
        assertArrayEquals("Throwable changed",
            orig.getThrown() == null ? null : orig.getThrownProxy().getExtendedStackTrace(),
            changed.getThrown() == null ? null : changed.getThrownProxy().getExtendedStackTrace()
        );
        assertEquals("ContextMap changed", orig.getContextMap(), changed.getContextMap());
        assertEquals("ContextStack changed", orig.getContextStack(), changed.getContextStack());
        assertEquals("ThreadName changed", orig.getThreadName(), changed.getThreadName());
        assertEquals("Source changed", orig.getSource(), changed.getSource());
        assertEquals("Millis changed", orig.getTimeMillis(), changed.getTimeMillis());
    }