Possible NPE in HcHttpProbe

[panthony]

Offending piece of code:

    public Map<String, Number> getNewSampleValues() {
        log(Level.DEBUG, "Getting %s", getUrl());
        HttpClientStarter httpstarter = find(HttpClientStarter.class);
        HttpClient cnx = httpstarter.getHttpClient();

The method find() may return NULL if the class is not found.