drowl_paragraphs_update_8310 fails with custom theme

This is a combination of

/**
 * Recalculate breakpoint_mapping_sizes values.
 */
function drowl_paragraphs_update_8310(&$sandbox) {
  $configEditable = \Drupal::service('config.factory')->getEditable('drowl_paragraphs.settings');
  $breakpoint_mapping = $configEditable->get('breakpoint_mapping');
  $breakpoint_mapping_sizes = \Drupal\drowl_paragraphs\Form\DrowlParagraphsSettingsForm::breakpointMappingToDeviceSizes($breakpoint_mapping);
  $configEditable->set('breakpoint_mapping_sizes', $breakpoint_mapping_sizes)->save();

  return 'Updated breakpoint mapping sizes';
}

and

breakpoint_group: drowl_base
breakpoint_mapping:
  drowl_base:
    small:
      1x:
        size_mapping: sm
    medium:
      1x:
        size_mapping: md
    large:
      1x:
        size_mapping: lg
    xlarge:
      1x:
        size_mapping: lg
    xxlarge:
      1x:
        size_mapping: lg

breakpoint_group: drowl_base
breakpoint_mapping:
drowl_base:

Which means this is a hard coded dependency on the breakpoint mapping from drowl_base.
Without that it won't work. We can just skip the step, if it does not exist.

We decided to do this in former times, because we can't cleanly rely on breakpoints to exist.

I don't think this is worth fixing any more with drowl_paragraphs_bs but let's keep this postponed for visibility reasons, if we should run into this again.