Fix NPE in FileObserver when multiple events pile in for a defunct

        public void onEvent(int wfd, int mask, String path) {

            // look up our observer, fixing up the map if necessary...

        FileObserver observer;

            FileObserver observer = null;

            synchronized (m_observers) {

                WeakReference weak = m_observers.get(wfd);

                if (weak != null) {  // can happen with lots of events from a dead wfd

                    observer = (FileObserver) weak.get();

                    if (observer == null) {

                        m_observers.remove(wfd);

                    }

                }

            }

            // ...then call out to the observer without the sync lock held

            if (observer != null) {