Empty strings ("") passed in as contextual filter argument aren't considered missing

Problem/Motivation

If an empty string ("") is passed in as contextual filter argument, it isn't considered a missing argument but is filtered against.

This was raised before in #2815863: Contextual filter values of "" don't trigger "When the filter value is NOT available" against D7 Views module, and originally came up in #1699378-20: Allow tokens in entity reference views selection arguments and was considered a Views (now: Core) bug in #1699378-94: Allow tokens in entity reference views selection arguments.

Steps to reproduce

Example:

      $arguments = [ 
        0 => '', // is processed in query
        1 => NULL, // is skipped and default argument or default action is used
        2 => 'foo' // is processed in query
      ];

      /** @var \Drupal\views\ViewExecutable $view */
      $view = Views::getView($target_id);
      $view->setArguments($arguments);
      $view->preExecute();
      $view->execute();

An empty string as argument could be an result of a token replacement like this:

$value = '[node:field_with_no_user_input]';
$token_data = [$entity->getEntityTypeId() => $entity];
$token_service = \Drupal::token();
$arguments[] = $token_service->replace($value, $token_data);

Proposed resolution

I think sanitizing the empty string to no argument given is the expected behavior. We should however think twice making sure there really isn't a usecase for the current behavior resp. no sitebuilder's assumption might be broken.

Remaining tasks

TBD

User interface changes

TBD

API changes

TBD

Data model changes

TBD

Release notes snippet

TBD