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Add class to block in page or node preprocessor

I want to add a class to the page tile block of specific node types so as to conditionally show and hide it. I arrive at this (page preprocessor already exist, added ‘add class to page_title block to hide & show’ to achieve the show/hide):

use DrupalComponentUtilityHtml; use DrupalCoreTemplateAttribute; use DrupalnodeNodeInterface; use DrupalnodeEntityNode;  /**  * Implements template_preprocess_page().  */ function bd_classy_preprocess_page(&$variables) {   if (isset($variables['node'])) {     $node = $variables['node'];     // Adds additional classes.     if ($node && is_int($node)) {       $node = Node::load($node);     }      if ($node instanceof NodeInterface) {       $path = 'path' . Html::cleanCssIdentifier($node->toUrl()->toString());       $variables['attributes']['class'][] = $node->getType();       $variables['attributes']['class'][] = $path;        //add class to page_title block to hide & show        if (         $node->hasField('field_hide_title') && ($node->getType() == 'cage' ||           $node->getType() == 'over_land')       ) {          $block = DrupalblockEntityBlock::load($variables['elements']['#id']);          if ($block == 'bd_classy_page_title' && $node->get('field_hide_title')->value == 1) {           $variables['attributes']['class'][] = 'visually-hidden';         } else {           $variables['attributes']['class'][] = 'visible';         }       } else {         $variables['attributes']['class'][] = 'visually-hidden';       } // end adding class      }   } }

It’s not working and I’ve got these errors in log:

Checked log messages and found these:

- Notice: Undefined index: elements in bb_classy_preprocess_page() (line 38 of /var/www/html/web/themes/custom/bd_classy/bd_classy.theme)  - Notice: Trying to access array offset on value of type null in bd_classy_preprocess_page() (line 38 of /var/www/html/web/themes/custom/bd_classy/bd_classy.theme)  - Warning: assert(): Cannot load the "block" entity with NULL ID. failed in DrupalCoreEntityEntityStorageBase->load() (line 295 of /var/www/html/web/core/lib/Drupal/Core/Entity/EntityStorageBase.php)  - Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalCoreEntityEntityStorageBase->loadMultiple() (line 312 of /var/www/html/web/core/lib/Drupal/Core/Entity/EntityStorageBase.php)
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Add class to block in page or node preprocessor

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