Steps to reproduce
TypeError: key(): Argument #1 ($array) must be of type array, null given in key() (line 424 of modules\contrib\entity_browser\src\Plugin\Field\FieldWidget\EntityReferenceBrowserWidget.php).
Drupal\entity_browser\Plugin\Field\FieldWidget\EntityReferenceBrowserWidget::processEntityBrowser(Array, Object, Array)
call_user_func_array(Array, Array) (Line: 1013)
Drupal\Core\Form\FormBuilder->doBuildForm('question_entity_text_question_add_form', Array, Object) (Line: 1076)
Drupal\Core\Form\FormBuilder->doBuildForm('question_entity_text_question_add_form', Array, Object) (Line: 1076)
Drupal\Core\Form\FormBuilder->doBuildForm('question_entity_text_question_add_form', Array, Object) (Line: 1076)
Drupal\Core\Form\FormBuilder->doBuildForm('question_entity_text_question_add_form', Array, Object) (Line: 579)
Drupal\Core\Form\FormBuilder->processForm('question_entity_text_question_add_form', Array, Object) (Line: 325)
Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 73)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 627)
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: 181)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
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: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
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: 704)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)