How do I check if a LevelPtr is null ?

I'm running into a problem when I get a logger that is not in my
configuration file. The logger appears to be created with a
null Level. How can I check if the level is null so I can
set it to a default value ? Thanks.

e.g.

log4cxx::PropertyConfigurator::configure("some-config-filename");
LoggerPtr logger = log4cxx::Logger::getLogger("some-logger-name");
LevelPtr level = logger->getLevel();

/* at this point it looks like level's private "p" member is null */