Hide accordion if contained fields are empty/have no content

Thanks for this, patch in #5 works great. The only issue i see is that there is no obvious definition of which tab is which (other than looking at the text of the tab's A tag - which in some use cases may not be good option). For example I have 4 tabs, any of which may be empty/hidden. But the tabs aren't numbered 1, 2, 4 if 3 is hidden; they are always renumbered 1, 2, 3. This makes it harder to know which is hidden.

I think it would be better if 3 is hidden, then 3 is left out.

looking at code though i suspect tricky to redo how this is numbered. I do see weight is maintained and carried through to twig so this was usable to solve my problem:

function mytheme_preprocess_lb_tabs_tabs(&$variables) {
  $variables['content']['weight'] = [];
  foreach ($variables['content']['content_blocks'] as $block) {
    if (isset($block['#weight'])) {
      $variables['content']['weight'][] = $block['#weight'];
    }
  }
}

and then in tpl, change content loop to:

      {% for contentKey, contentBlock in content.content_blocks if contentKey|first != '#' %}
        <div id="{{ "#{settings.dom_id}-#{loop.index}" }}" class="toc-ignore-{{content.weight[loop.index0]}}">
          {{ contentBlock }}
        </div>
      {% endfor %}

When i tested the patch in #5 and said it worked I only had a simple field added to my tabs; and if the field was empty, this does work. But my real case is a block in the tab which contains other blocks (like mini-panels used to be). In this case, even with all the inside blocks empty the patch still results in an empty tab being shown.

I can see this not being the way to go here; but i needed this to make empty tabs not show:

    // Remove empty blocks
    foreach (Element::children($build['content_blocks'], TRUE) as $i => $contentKey) {
      $contents = trim(strip_tags(\Drupal::service('renderer')->renderRoot($build['content_blocks'][$contentKey]['content'])));
      if (!$contents) {
        unset($build['content_blocks'][$contentKey]);
      }
    }