activities: Properly return activities to the callback.

The empty ArrayList that was passed back before was just there to test the behaviour of the Activities activity when an empty data set was returned.

src/main/java/com/owncloud/android/ui/activities/data/ActivitiesServiceApiImpl.java

@@ -107,7 +107,7 @@ public class ActivitiesServiceApiImpl implements ActivitiesServiceApi {
         protected void onPostExecute(Boolean success) {
             super.onPostExecute(success);
             if (success) {
-                mCallback.onLoaded(new ArrayList<>(), ownCloudClient, mPageUrl == null);
+                mCallback.onLoaded(mActivities, ownCloudClient, mPageUrl == null);
             }
             mCallback.onError(errorMessage);
         }