fix NPE when dump wins the race against emit

            finalImportance = new ImportanceHistogram(context, "note_importance_");

        }

        public AggregatedStats getPrevious() {

            if (mPrevious == null) {

                mPrevious = new AggregatedStats(mContext, key);

            }

            return mPrevious;

        }

        public void countApiUse(NotificationRecord record) {

            final Notification n = record.getNotification();

            if (n.actions != null) {

        }

        public void emit() {

            if (mPrevious == null) {

                mPrevious = new AggregatedStats(null, key);

            }

            maybeCount("note_post", (numPostedByApp - mPrevious.numPostedByApp));

            maybeCount("note_update", (numUpdatedByApp - mPrevious.numUpdatedByApp));

            maybeCount("note_remove", (numRemovedByApp - mPrevious.numRemovedByApp));

            maybeCount("note_with_people", (numWithValidPeople - mPrevious.numWithValidPeople));

            maybeCount("note_with_stars", (numWithStaredPeople - mPrevious.numWithStaredPeople));

            maybeCount("people_cache_hit", (numPeopleCacheHit - mPrevious.numPeopleCacheHit));

            maybeCount("people_cache_miss", (numPeopleCacheMiss - mPrevious.numPeopleCacheMiss));

            maybeCount("note_blocked", (numBlocked - mPrevious.numBlocked));

            maybeCount("note_suspended", (numSuspendedByAdmin - mPrevious.numSuspendedByAdmin));

            maybeCount("note_with_actions", (numWithActions - mPrevious.numWithActions));

            maybeCount("note_private", (numPrivate - mPrevious.numPrivate));

            maybeCount("note_secret", (numSecret - mPrevious.numSecret));

            maybeCount("note_interupt", (numInterrupt - mPrevious.numInterrupt));

            maybeCount("note_big_text", (numWithBigText - mPrevious.numWithBigText));

            maybeCount("note_big_pic", (numWithBigPicture - mPrevious.numWithBigPicture));

            maybeCount("note_fg", (numForegroundService - mPrevious.numForegroundService));

            maybeCount("note_ongoing", (numOngoing - mPrevious.numOngoing));

            maybeCount("note_auto", (numAutoCancel - mPrevious.numAutoCancel));

            maybeCount("note_large_icon", (numWithLargeIcon - mPrevious.numWithLargeIcon));

            maybeCount("note_inbox", (numWithInbox - mPrevious.numWithInbox));

            maybeCount("note_media", (numWithMediaSession - mPrevious.numWithMediaSession));

            maybeCount("note_title", (numWithTitle - mPrevious.numWithTitle));

            maybeCount("note_text", (numWithText - mPrevious.numWithText));

            maybeCount("note_sub_text", (numWithSubText - mPrevious.numWithSubText));

            maybeCount("note_info_text", (numWithInfoText - mPrevious.numWithInfoText));

            noisyImportance.maybeCount(mPrevious.noisyImportance);

            quietImportance.maybeCount(mPrevious.quietImportance);

            finalImportance.maybeCount(mPrevious.finalImportance);

            mPrevious.numPostedByApp = numPostedByApp;

            mPrevious.numUpdatedByApp = numUpdatedByApp;

            mPrevious.numRemovedByApp = numRemovedByApp;

            mPrevious.numPeopleCacheHit = numPeopleCacheHit;

            mPrevious.numPeopleCacheMiss = numPeopleCacheMiss;

            mPrevious.numWithStaredPeople = numWithStaredPeople;

            mPrevious.numWithValidPeople = numWithValidPeople;

            mPrevious.numBlocked = numBlocked;

            mPrevious.numSuspendedByAdmin = numSuspendedByAdmin;

            mPrevious.numWithActions = numWithActions;

            mPrevious.numPrivate = numPrivate;

            mPrevious.numSecret = numSecret;

            mPrevious.numInterrupt = numInterrupt;

            mPrevious.numWithBigText = numWithBigText;

            mPrevious.numWithBigPicture = numWithBigPicture;

            mPrevious.numForegroundService = numForegroundService;

            mPrevious.numOngoing = numOngoing;

            mPrevious.numAutoCancel = numAutoCancel;

            mPrevious.numWithLargeIcon = numWithLargeIcon;

            mPrevious.numWithInbox = numWithInbox;

            mPrevious.numWithMediaSession = numWithMediaSession;

            mPrevious.numWithTitle = numWithTitle;

            mPrevious.numWithText = numWithText;

            mPrevious.numWithSubText = numWithSubText;

            mPrevious.numWithInfoText = numWithInfoText;

            noisyImportance.update(mPrevious.noisyImportance);

            quietImportance.update(mPrevious.quietImportance);

            finalImportance.update(mPrevious.finalImportance);

            AggregatedStats previous = getPrevious();

            maybeCount("note_post", (numPostedByApp - previous.numPostedByApp));

            maybeCount("note_update", (numUpdatedByApp - previous.numUpdatedByApp));

            maybeCount("note_remove", (numRemovedByApp - previous.numRemovedByApp));

            maybeCount("note_with_people", (numWithValidPeople - previous.numWithValidPeople));

            maybeCount("note_with_stars", (numWithStaredPeople - previous.numWithStaredPeople));

            maybeCount("people_cache_hit", (numPeopleCacheHit - previous.numPeopleCacheHit));

            maybeCount("people_cache_miss", (numPeopleCacheMiss - previous.numPeopleCacheMiss));

            maybeCount("note_blocked", (numBlocked - previous.numBlocked));

            maybeCount("note_suspended", (numSuspendedByAdmin - previous.numSuspendedByAdmin));

            maybeCount("note_with_actions", (numWithActions - previous.numWithActions));

            maybeCount("note_private", (numPrivate - previous.numPrivate));

            maybeCount("note_secret", (numSecret - previous.numSecret));

            maybeCount("note_interupt", (numInterrupt - previous.numInterrupt));

            maybeCount("note_big_text", (numWithBigText - previous.numWithBigText));

            maybeCount("note_big_pic", (numWithBigPicture - previous.numWithBigPicture));

            maybeCount("note_fg", (numForegroundService - previous.numForegroundService));

            maybeCount("note_ongoing", (numOngoing - previous.numOngoing));

            maybeCount("note_auto", (numAutoCancel - previous.numAutoCancel));

            maybeCount("note_large_icon", (numWithLargeIcon - previous.numWithLargeIcon));

            maybeCount("note_inbox", (numWithInbox - previous.numWithInbox));

            maybeCount("note_media", (numWithMediaSession - previous.numWithMediaSession));

            maybeCount("note_title", (numWithTitle - previous.numWithTitle));

            maybeCount("note_text", (numWithText - previous.numWithText));

            maybeCount("note_sub_text", (numWithSubText - previous.numWithSubText));

            maybeCount("note_info_text", (numWithInfoText - previous.numWithInfoText));

            noisyImportance.maybeCount(previous.noisyImportance);

            quietImportance.maybeCount(previous.quietImportance);

            finalImportance.maybeCount(previous.finalImportance);

            previous.numPostedByApp = numPostedByApp;

            previous.numUpdatedByApp = numUpdatedByApp;

            previous.numRemovedByApp = numRemovedByApp;

            previous.numPeopleCacheHit = numPeopleCacheHit;

            previous.numPeopleCacheMiss = numPeopleCacheMiss;

            previous.numWithStaredPeople = numWithStaredPeople;

            previous.numWithValidPeople = numWithValidPeople;

            previous.numBlocked = numBlocked;

            previous.numSuspendedByAdmin = numSuspendedByAdmin;

            previous.numWithActions = numWithActions;

            previous.numPrivate = numPrivate;

            previous.numSecret = numSecret;

            previous.numInterrupt = numInterrupt;

            previous.numWithBigText = numWithBigText;

            previous.numWithBigPicture = numWithBigPicture;

            previous.numForegroundService = numForegroundService;

            previous.numOngoing = numOngoing;

            previous.numAutoCancel = numAutoCancel;

            previous.numWithLargeIcon = numWithLargeIcon;

            previous.numWithInbox = numWithInbox;

            previous.numWithMediaSession = numWithMediaSession;

            previous.numWithTitle = numWithTitle;

            previous.numWithText = numWithText;

            previous.numWithSubText = numWithSubText;

            previous.numWithInfoText = numWithInfoText;

            noisyImportance.update(previous.noisyImportance);

            quietImportance.update(previous.quietImportance);

            finalImportance.update(previous.finalImportance);

        }

        void maybeCount(String name, int value) {

        }

        public JSONObject dumpJson() throws JSONException {

            AggregatedStats previous = getPrevious();

            JSONObject dump = new JSONObject();

            dump.put("key", key);

            dump.put("duration", SystemClock.elapsedRealtime() - mCreated);

            maybePut(dump, "numWithText", numWithText);

            maybePut(dump, "numWithSubText", numWithSubText);

            maybePut(dump, "numWithInfoText", numWithInfoText);

            noisyImportance.maybePut(dump, mPrevious.noisyImportance);

            quietImportance.maybePut(dump, mPrevious.quietImportance);

            finalImportance.maybePut(dump, mPrevious.finalImportance);

            noisyImportance.maybePut(dump, previous.noisyImportance);

            quietImportance.maybePut(dump, previous.quietImportance);

            finalImportance.maybePut(dump, previous.finalImportance);

            return dump;

        }