Hide block if empty not working

I've found the issue:

On line 620 of HierarchicalTaxonomyMenuBlock.php, the following check is performed:

if ($this->configuration['hide_block'] && !$vocabulary_tree) {
  return [];
}

However, the code then proceeds to build a $vocabulary_tree_array, only then excluding 'empty' terms, as seen on line 642:

if (!empty($this->configuration['exclude_empty_terms']) && empty($entities)) {
  continue;
}

The check to hide the block should be done on $vocabulary_tree_array after it's generated, not before it's generated.

I created a simple patch which clears up the issue in my case.