Steps to reproduce
create any entity and add entity browser table then showing error.
TypeError: Drupal\entity_browser_table\Plugin\Field\FieldWidget\EntityReferenceBrowserTableWidget::getFirstColumn(): Return value must be of type array, null returned in Drupal\entity_browser_table\Plugin\Field\FieldWidget\EntityReferenceBrowserTableWidget->getFirstColumn() (line 291 of modules\contrib\entity_browser_table\src\Plugin\Field\FieldWidget\EntityReferenceBrowserTableWidget.php).
Drupal\entity_browser_table\Plugin\Field\FieldWidget\EntityReferenceBrowserTableWidget->getFirstColumn(Object) (Line: 170)
Drupal\entity_browser_table\Plugin\Field\FieldWidget\EntityReferenceBrowserTableWidget->buildTableRows(Array, 'edit-field-questions', Array) (Line: 109)
Drupal\entity_browser_table\Plugin\Field\FieldWidget\EntityReferenceBrowserTableWidget->displayCurrentSelection('edit-field-questions', Array, Array) (Line: 415)
Drupal\entity_browser\Plugin\Field\FieldWidget\EntityReferenceBrowserWidget->formElement(Object, 0, Array, Array, Object) (Line: 79)
Drupal\entity_browser_table\Plugin\Field\FieldWidget\EntityReferenceBrowserTableWidget->formElement(Object, 0, Array, Array, Object) (Line: 353)
Drupal\Core\Field\WidgetBase->formSingleElement(Object, 0, Array, Array, Object) (Line: 92)
Drupal\Core\Field\WidgetBase->form(Object, Array, Object) (Line: 183)
Drupal\Core\Entity\Entity\EntityFormDisplay->buildForm(Object, Array, Object) (Line: 121)
Drupal\Core\Entity\ContentEntityForm->form(Array, Object) (Line: 127)
Drupal\node\NodeForm->form(Array, Object) (Line: 106)
Drupal\Core\Entity\EntityForm->buildForm(Array, Object)
call_user_func_array(Array, Array) (Line: 536)
Drupal\Core\Form\FormBuilder->retrieveForm('node_testlets_edit_form', Object) (Line: 283)
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: 580)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 169)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 81)
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: 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: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 718)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)