Undefined index: auto_placeholder_conditions

Problem/Motivation

PHP notice:

Notice: Undefined index: auto_placeholder_conditions in Drupal\Core\Render\Renderer->shouldAutomaticallyPlaceholder() (line 657 of core/lib/Drupal/Core/Render/Renderer.php).

Steps to reproduce

1. Set Error reporting to 'All messages' at admin/config/development/logging
2. drush cr
3. Visit the home page

Proposed resolution

t.b.d.

Remaining tasks

User interface changes

none

API changes

none, i think

Data model changes

none, i think