Reported in: https://www.drupal.org/project/drupal/issues/2809635#comment-12432197
From issue:
==============
+++ b/core/profiles/demo_umami/themes/umami/templates/layout/page.html.twig
@@ -0,0 +1,132 @@
+ {% if page.header|render|striptags|trim is not empty %}
...
+ {% if page.tabs|render|striptags|trim is not empty %}
...
+ {% if page.banner_top|render|striptags|trim is not empty %}
...
+ {% if page.breadcrumbs|render|striptags|trim is not empty %}
...
+ {% if page.page_title|render|striptags|trim is not empty %}
...
+ {% if page.sidebar|render|striptags|trim is not empty %}
...
+ {% if page.footer|render|striptags|trim is not empty %}
...
+ {% if page.bottom|render|striptags|trim is not empty %}
Is this the only way we can do this? Surely we can do something smarter in preprocessing?
==============
If we just print
{% if page.tabs %}
{{ pagetabs }}
{% endif %}
We get empty regions printed on every page that there is no block in that region for. So on a views page, we'll have<div class="region-tabs"></div>
This is a known issue in Drupal core, so we can't fix it until that is fixed.
https://www.drupal.org/node/953034