Skip empty lines in test url list.

        //read from BufferedReader instead of populating a list in advance,

        //this will avoid excessive memory usage in case of a large list

        while((url = listReader.readLine()) != null) {

            url = url.trim();

            if(url.length() == 0)

                continue;

            start = System.currentTimeMillis();

            Log.v(LOGTAG, "Testing URL: " + url);

            updateTestStatus(url);