Array support removed from function Merge::key in Drupal 11

Problem/Motivation

Views Natural Sort causes HTTP errors when uploading files or running AJAX processes on a Drupal 11 site.

Steps to reproduce

Drupal 11 site with Views Natural Sort installed and configured on at least one view.

Navigate to Administration > Structure > Views > Views Settings > View Natural Sort Configuration.

Select In case of Emergency > Rebuild Index.

This can also be reproduced when uploading files or running AJAX operations unrelated to Views Natural Sort. This AJAX HTTP error prevents these operations from completing. When Views Natural Sort is uninstalled, no errors occur.

An AJAX HTTP error occurred.
HTTP Result Code: 500
Debugging information follows.
Path: /batch?id=98&op=do_nojs&op=do
StatusText: error
ResponseText: The website encountered an unexpected error. Try again later.TypeError: Cannot access offset of type array on array in Drupal\Core\Database\Query\Merge->key() (line 331 of core/lib/Drupal/Core/Database/Query/Merge.php). Drupal\views_natural_sort\IndexRecord->save() (Line: 329)
Drupal\views_natural_sort\ViewsNaturalSortService->storeIndexRecordsFromEntity(Object) (Line: 61)
Drupal\views_natural_sort\Plugin\QueueWorker\EntityIndexer->processItem(Array) (Line: 210)
views_natural_sort_rebuild_index('views_natural_sort_entity_index', Array) (Line: 297)
_batch_process() (Line: 139)
_batch_do() (Line: 95)
_batch_page(Object) (Line: 52)
Drupal\system\Controller\BatchController->batchPage(Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 593)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 121)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 183)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 44)
Drupal\redirect_after_login\RedirectMiddleware->handle(Object, 1, 1) (Line: 53)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle(Object, 1, 1) (Line: 32)
Drupal\big_pipe\StackMiddleware\ContentLength->handle(Object, 1, 1) (Line: 116)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 90)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 36)
Drupal\Core\StackMiddleware\AjaxPageState->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle(Object, 1, 1) (Line: 709)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)