NPE when subject is null

[n-belokopytov]

Crash

 Caused by: java.lang.NullPointerException
        at com.snowplowanalytics.snowplow.tracker.Tracker.addDefaultContextData(Tracker.java:180)
        at com.snowplowanalytics.snowplow.tracker.Tracker.completePayload(Tracker.java:149)
        at com.snowplowanalytics.snowplow.tracker.Tracker.trackUnstructuredEvent(Tracker.java:371)
        at com.snowplowanalytics.snowplow.tracker.Tracker.trackScreenView(Tracker.java:585)
        at com.snowplowanalytics.snowplow.tracker.Tracker.trackScreenView(Tracker.java:547)
        at com.chefsfeed.Analytics.activityStart(Analytics.java:191)

This is the code of tracker creation

        RequestCallback callback = new RequestCallback() {
            @Override
            public void onSuccess(int successCount) {
                Log.d(TAG, "Buffer length for POST/GET:" + successCount);
            }
            @Override
            public void onFailure(int successCount, int failureCount) {
                Log.d(TAG, "Failures: " + failureCount + "; Successes: " + successCount);
            }
        };

        Emitter e2 = new Emitter
                .EmitterBuilder("com.chefsfeed", context)
                .callback(callback)
                .build();

        // Create a Tracker with all options
        mTracker = new Tracker
                .TrackerBuilder(e2, context.getPackageName(), context.getApplicationInfo().name)
                .base64(true) // Optional - defines if we use base64 encoding
                .platform(DevicePlatforms.Mobile) // Optional - defines what platform the event will report to be on
                .build();

Notice the absence of an optional subject setter.

NPE is raised during trackScreenView in
String idScreen = cfActivity.getClass().getCanonicalName();
tracker.trackScreenView(cfActivity.getActivityName(), idScreen);

[jbeemster]

Thanks for raising @n-belokopytov. I need to wrap a check for Subject == Null around this block: https://github.com/snowplow/snowplow-android-tracker/blob/master/snowplow-android-tracker/src/main/java/com/snowplowanalytics/snowplow/tracker/Tracker.java#L180-L189