Prevent empty views blocks from getting rendered even if they are empty.

<?php

use Drupal\views\Plugin\Block\ViewsBlock;

/**
 * Implements hook_block_alter().
 */
function hook_block_alter(array &$definitions) {
  foreach ($definitions as $block_id => &$block_definition) {
    if ($block_definition['class'] === ViewsBlock::class) {
      $block_definition['class'] = 'Drupal\my_module\Plugin\Block\ViewsBlock';
    }
  }
}

<?php

namespace Drupal\my_module\Plugin\Block;

use Drupal\views\Plugin\Block\ViewsBlock as ViewsBlockCore;

/**
 * Replaces the generic Views block.
 */
class ViewsBlock extends ViewsBlockCore {

  /**
   * {@inheritdoc}
   */
  public function build() {
    if (empty($this->view->result) && empty($this->view->empty)) {
      // Without caching.
      // return ['#cache' => ['max-age' => 0]];
      // With hard caching.
      return [];
    }

    return parent::build();
  }

}