code: @Override
      public void onError(final Throwable t) {
  
          Objects.requireNonNull(t);
          if (stream != null)
              ((Consumer) stream.getErrorHandler()
                      .orElse((Consumer) h -> {
                      })).accept(t);
          if (errorHandler != null)
              errorHandler.accept(t);
  
      }
docs: /* (non-Javadoc)
  @see org.reactivestreams.Subscriber#onError(java.lang.Throwable)