Merge pull request #51 from Leanplum/feature/fix-LP-5020

fix(PushService) add null checker for context and message.

Author: Enuviel

AndroidSDK/src/com/leanplum/LeanplumPushService.java

@@ -283,6 +283,10 @@ static void handleNotification(final Context context, final Bundle message) {
    * Put the message into a notification and post it.
    */
   private static void showNotification(Context context, Bundle message) {
+    if (context == null || message == null) {
+      return;
+    }
+
     NotificationManager notificationManager = (NotificationManager)
         context.getSystemService(Context.NOTIFICATION_SERVICE);