Error when trying to delete a revision

Problem/Motivation

My site is running drupal 8.9.13, and Node Revision Delete v. 8.x-1.x-dev. When trying to manually delete a revision from the Revisions tab, I get the following error:

The website encountered an unexpected error. Please try again later.
Error: Call to a member function id() on string in node_revision_delete_form_node_revision_delete_confirm_alter() (line 192 of modules/contrib/node_revision_delete/node_revision_delete.module).
node_revision_delete_form_node_revision_delete_confirm_alter(Array, Object, 'node_revision_delete_confirm') (Line: 539)
Drupal\Core\Extension\ModuleHandler->alter('form', Array, Object, 'node_revision_delete_confirm') (Line: 836)
Drupal\Core\Form\FormBuilder->prepareForm('node_revision_delete_confirm', Array, Object) (Line: 244)
Drupal\autosave_form\Form\AutosaveFormBuilder->prepareForm('node_revision_delete_confirm', Array, Object) (Line: 279)
Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 97)
Drupal\autosave_form\Form\AutosaveFormBuilder->buildForm(Object, Object) (Line: 91)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 573)
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: 151)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 68)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
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: 50)
Drupal\ban\BanMiddleware->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 52)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 708)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Steps to reproduce

Go to Content menu and open Revision tab of any content.
Try to delete a revision.

Not sure what's going on, but this is a really useful module so hope a fix is possible soon. Thanks!