BadRequestException: entity_browser_select expects array, got string — incompatible with Symfony 7 (3.0.0) [#3612158]

Problem/Motivation

In ckeditor5_entity_browser 3.0.0, clicking "Insert" in the entity browser dialog throws a fatal error and the modal does not close:

Symfony\Component\HttpFoundation\Exception\BadRequestException:
Unexpected value for parameter "entity_browser_select": expecting "array", got "string".
in Symfony\Component\HttpFoundation\ParameterBag->all()
(line 52 of vendor/symfony/http-foundation/ParameterBag.php)

ckeditor5_entity_browser.module uses $request->request->all('entity_browser_select') to read the POST value. In Symfony 7 (shipped with Drupal 11), ParameterBag::all(key) strictly requires the value to be an array — it throws BadRequestException immediately when a scalar string is submitted. The fallback get() call is never reached.

Steps to reproduce

1. Install drupal/ckeditor5_entity_browser 3.0.0 on Drupal 11 (Symfony 7)
2. Open any node edit form with a CKEditor 5 body field
3. Click "Insert Media" in the toolbar
4. Select a media item and click "Insert selected"
5. → BadRequestException is thrown; modal does not close

Proposed resolution

Replace the all() call with get() and normalize the value to an array manually, handling both scalar string and array input:

$raw_selection = $request->request->get('entity_browser_select');
if (is_array($raw_selection)) {
  $selection = $raw_selection;
}
elseif (!empty($raw_selection)) {
  $selection = [$raw_selection];
}
else {
  $selection = [];
}
$selection = array_filter($selection);

This is backward-compatible: array submissions (multi-select widgets) continue to work via the is_array() branch, while scalar string submissions are safely wrapped into an array.