Display anywhere facet does not check if source is available

Problem/Motivation

Having an enabled facet block that is set to be displayed on any page does not check that the search is (still) available. For example if it's been disabled. Search API itself shows a nice "Cannot search on a disabled index". Facet API throws a fatal:

Drupal\Component\Plugin\Exception\PluginNotFoundException: The "search_api:views_embed__view__display" plugin does not exist. Valid plugin IDs for Drupal\facets\FacetSource\FacetSourcePluginManager are: in Drupal\Core\Plugin\DefaultPluginManager->doGetDefinition() (line 53 of core/lib/Drupal/Component/Plugin/Discovery/DiscoveryTrait.php).                                                                                    
                                                                                                                                                                                                                    
Drupal\Core\Plugin\DefaultPluginManager->getDefinition('search_api:views_embed__view__display') (Line: 16)                                                                                                          
Drupal\Core\Plugin\Factory\ContainerFactory->createInstance('search_api:views_embed__view__display', Array) (Line: 83)                                                                                              
Drupal\Component\Plugin\PluginManagerBase->createInstance('search_api:views_embed__view__display') (Line: 463)                                                                                                      
Drupal\facets\FacetManager\DefaultFacetManager->updateResults('search_api:views_embed__view__display') (Line: 250)                                                                                                  
Drupal\facets\FacetManager\DefaultFacetManager->processFacets('search_api:views_embed__view__display') (Line: 327)                                                                                                  
Drupal\facets\FacetManager\DefaultFacetManager->processBuild(Object) (Line: 387)                                                                                                                                    
Drupal\facets\FacetManager\DefaultFacetManager->build(Object) (Line: 90)                                                                                                                                            
Drupal\facets\Plugin\Block\FacetBlock->build() (Line: 171) 

Steps to reproduce

• Create a search, view
• Create a facet. Configure the to display on all pages.
• Enable the block to be displayed.
• Then disable the search.
• Visit a page where the block would be rendered.

Proposed resolution

I think it could be as simple as https://git.drupalcode.org/issue/facets-3311856/-/commit/765d5ef4228906c...
$facet->getFacetSource() is needed no matter if it is on the page itself or elsewhere. It isn't returned if the index isn't available for whatever reason.