Error: Call to a member function bundle() on null in ParagraphViewBuilder

Problem/Motivation

Hey.
After updating Paragraphs from 8.x-1.0 to the latest dev we got the following error:
Error: Call to a member function bundle() on null in Drupal\paragraphs\ParagraphViewBuilder->buildMultiple() (line 21 of modules/contrib/paragraphs/src/ParagraphViewBuilder.php).

It seems like there isn't any check about what's in $build_list (as it's done in EntityViewBuilder).
We are using something similar to the code below to add the rendered output of some paragraphs to our Solr index.

Steps to reproduce

<?php
// Guess we have an entity with "field_paragraphs" containing multiple items ...
$paragraphs = $entity->field_paragraphs->referencedEntities();
$first_entity = reset($paragraphs);
$bundle = $first_paragraph->bundle();
$view_builder = \Drupal::entityTypeManager()->getViewBuilder($first_paragraph->getEntityTypeId());
// Create the build list.
$build = $view_builder->viewMultiple($paragraphs, 'teaser');
// Render items.
$rendered_output = (string) $this->getRenderer()->renderPlain($build);
?>

Proposed resolution

Loop through valid children of $build_list only.

Remaining tasks

* create patch