Passing NULL as the $elements value in RendererInterface::render() is deprecated

Passing NULL as the value for the $elements parameter in RendererInterface::render() is deprecated in Drupal 11.2.3 and will not be supported in Drupal 12.0.0.

Type declarations will be added to the $element parameter in the method signature in Drupal 12.0.0, so that it will look like this:
public function render(array &$elements)

Note that the $is_root_call parameter was previously deprecated in 11.2.0 and will be removed in Drupal 12.0.0. See this change record.