title: RxJava2 Flowable do not call to onNext method in Subscriber
body: <p>I'm new in rxjava and i have problem with Flowable.
  When <code>onComplete</code> method has called in <code>flatMap</code>, <code>onNext</code> method in subscriber not called. What's wrong here?. Have any suggestion? </p>
  
  <pre><code>        ResourceSubscriber&lt;List&lt;Song&gt;&gt; subscriber = new ResourceSubscriber&lt;List&lt;Song&gt;&gt;() {
          @Override
          public void onStart() {
              Log.e(TAG, "onStart");
              mView.showProgress();
          }
  
          @Override
          public void onNext(List&lt;Song&gt; songs) {
              mView.onLocalMusicLoaded(songs);
              mView.emptyView(songs.isEmpty());
              Log.e(TAG, "onNext");
              //Not call here after onComplete called
          }
  
          @Override
          public void onError(Throwable t) {
              mView.hideProgress();
              Log.e(TAG, "onError: ", t);
          }
  
          @Override
          public void onComplete() {
              mView.hideProgress();
              Log.e(TAG, "onComplete");
          }
      };
  
  
      Disposable disposable = Flowable.just(cursor)
              .flatMap(new Function&lt;Cursor, Publisher&lt;List&lt;Song&gt;&gt;&gt;() {
                  @Override
                  public Publisher&lt;List&lt;Song&gt;&gt; apply(@NonNull Cursor cursor) throws Exception {
                      final List&lt;Song&gt; songs = new ArrayList&lt;&gt;();
                      if (cursor != null &amp;&amp; cursor.getCount() &gt; 0) {
                          cursor.moveToFirst();
                          do {
                              Song song = cursorToMusic(cursor);
                              songs.add(song);
                          } while (cursor.moveToNext());
                      }
                      return Flowable.create(new FlowableOnSubscribe&lt;List&lt;Song&gt;&gt;() {
                          @Override
                          public void subscribe(@NonNull FlowableEmitter&lt;List&lt;Song&gt;&gt; e) throws Exception {
                              e.onNext(songs);
                              e.onComplete();
                          }
                      }, BackpressureStrategy.LATEST);
                  }
              })
              .doOnNext(new Consumer&lt;List&lt;Song&gt;&gt;() {
                  @Override
                  public void accept(@NonNull List&lt;Song&gt; songs) throws Exception {
                      Log.e(TAG, "onLoadFinished doOnNext: " + songs.size());
                      Collections.sort(songs, new Comparator&lt;Song&gt;() {
                          @Override
                          public int compare(Song left, Song right) {
                              return left.getDisplayName().compareTo(right.getDisplayName());
                          }
                      });
                  }
              })
              .subscribeOn(Schedulers.io())
              .observeOn(AndroidSchedulers.mainThread())
              .subscribeWith(subscriber);
  
      mCompositeDisposable.add(disposable);
  </code></pre>