#vulnerable code 
                                @Test
    public void testResponseContentOverwriteHeaders() throws Exception {
        ResponseContent interceptor = new ResponseContent(true);
        HttpContext context = new BasicHttpContext(null);
        HttpResponse response = new BasicHttpResponse(HttpVersion.HTTP_1_1, HttpStatus.SC_OK, "OK");
        response.addHeader(new BasicHeader(HTTP.CONTENT_LEN, "10"));
        response.addHeader(new BasicHeader(HTTP.TRANSFER_ENCODING, "whatever"));
        interceptor.process(response, context);
        Assert.assertEquals("0", response.getFirstHeader(HTTP.CONTENT_LEN).getValue());
        Assert.assertEquals("whatever", response.getFirstHeader(HTTP.TRANSFER_ENCODING).getValue());
    } 
                            #location 10 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testResponseContentOverwriteHeaders() throws Exception {
        ResponseContent interceptor = new ResponseContent(true);
        HttpContext context = new BasicHttpContext(null);
        HttpResponse response = new BasicHttpResponse(HttpVersion.HTTP_1_1, HttpStatus.SC_OK, "OK");
        response.addHeader(new BasicHeader(HTTP.CONTENT_LEN, "10"));
        response.addHeader(new BasicHeader(HTTP.TRANSFER_ENCODING, "whatever"));
        interceptor.process(response, context);
        Assert.assertEquals("0", response.getFirstHeader(HTTP.CONTENT_LEN).getValue());
    }