@Test
    public void testNullMessage () {
        VespaFormatter formatter = new VespaFormatter(serviceName, app);
        LogRecord r = new LogRecord(LogLevel.ERROR, null);
        assertNotNull(r);
        try {
            String s = formatter.format(r);
            assertNotNull(s);
            assertTrue(s.indexOf("(empty)") > 0);
        }
        catch (NullPointerException e) {
            fail("unable to handle null message!");
        }
    }
Got a NullPointerException earlier when trying to format
a null message.  Added unit test to make sure this does
not happen again.  Makes sure that NullPointerException
is not thrown and that the formatted string contains the
expected message for saying that there was no log message.
vespalog/src/test/java/com/yahoo/log/VespaFormatterTestCase.java