Fix warning: Array to string conversion in Drupal\Component\Utility\Html::getClass()

Problem/Motivation

The view block title is outputed as an array like:

$output['#title'] = ['#markup' => $this->view->getTitle(), '#allowed_tags' => Xss::getHtmlTagList()];

When rendering a view block and displaying the view title, the next warning is shown
Warning: Array to string conversion in Drupal\Component\Utility\Html::getClass() (line 75 of core/lib/Drupal/Component/Utility/Html.php).
This warning cames from 'templates/BASE/components/00-theme/02-molecules/00-block/_block.twig' on line #87
where title (which is an array when is the title of a view) is passed as the argument to the clean_class filter.

Steps to reproduce

• Render a block view with a view title
• Check the id of the heading it will be like heading-array-20222906

Proposed resolution

Ensure the title is a string when is passed as argument to clean_class filter.