Undefined offset: 1 in paragraphs_preprocess_field_multiple_value_form()

Getting the following error after upgrading the lastest version of Paragraphs 8.x dev:

Notice: Undefined offset: 1 in paragraphs_preprocess_field_multiple_value_form() (line 284 of modules/paragraphs/paragraphs.module).
paragraphs_preprocess_field_multiple_value_form(Array, 'field_multiple_value_form', Array) (Line: 287)
Drupal\Core\Theme\ThemeManager->render('field_multiple_value_form', Array) (Line: 435)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 448)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 448)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 195)
Drupal\Core\Render\Renderer->render(Array, ) (Line: 226)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 574)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 227)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object, Object) (Line: 117)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object, Object) (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object, 'kernel.view', Object) (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch('kernel.view', Object) (Line: 149)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 64)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 99)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 78)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 50)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 656)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

The page is a node edit page with a paragraph attachment. If I remove the sole attached paragraph the error goes away. If I add it back again (with no values) the error returns.

If I roll back to the previous dev version of paragraphs (8.x-1.1+48-dev), the error goes away.

Looks like new code. This function doesn't exist in the previous version of paragraphs:

function paragraphs_preprocess_field_multiple_value_form(&$variables) {
  if (count($variables['element']['#field_parents']) === 0 && isset($variables['table']['#rows'])) {
    // Find header_action and move to header.
    // @see template_preprocess_field_multiple_value_form()
    foreach ($variables['table']['#rows'] as $i => $row) {
      if (isset($variables['table']['#rows'][$i]['data'][1]['data']['#attributes']['class'])) {
        if ($variables['table']['#rows'][$i]['data'][1]['data']['#attributes']['class'][1] === 'paragraphs-header-actions') {
          $variables['table']['#header'][0]['data'] = [
            'title' => $variables['table']['#header'][0]['data'],
            'button' => $variables['table']['#rows'][$i]['data'][1],
          ];
          unset($variables['table']['#rows'][$i]);
          break;
        }
      }
    }
  }
}

Digging into this with a bit of debug/kint, it looks like $variables['table']['#rows'][$i]['data'][1]['data']['#attributes']['class'] is an empty array for me. So it passes isset($variables['table']['#rows'][$i]['data'][1]['data']['#attributes']['class']), but $variables['table']['#rows'][$i]['data'][1]['data']['#attributes']['class'][1] is undefined.

If I make the logical change:

if (isset($variables['table']['#rows'][$i]['data'][1]['data']['#attributes']['class'])) {

and modify this to:

if (isset($variables['table']['#rows'][$i]['data'][1]['data']['#attributes']['class'][1])) {

The error goes away.

I could submit this as a patch, but I don't know enough about the new function to understand why it's there in the first place.