Merge pull request #16 from danpe/master

Fixed NPE when no tags available

Author: jkasten2

OneSignalSDK/onesignal/src/main/java/com/onesignal/OneSignal.java

@@ -729,7 +729,7 @@ void onFailure(int statusCode, String response, Throwable throwable) {
 
    public static void getTags(final GetTagsHandler getTagsHandler) {
       JSONObject tags = OneSignalStateSynchronizer.getTags();
-      if (tags.toString().equals("{}"))
+      if (tags == null || tags.toString().equals("{}"))
          getTagsHandler.tagsAvailable(null);
       else
          getTagsHandler.tagsAvailable(OneSignalStateSynchronizer.getTags());