Undefined index error at image fields with no preview style

Problem

I get an error while comparing two revisions when images changed, image thumbnail of the image field should be showed and no preview image style is set.

Notice: Undefined index: preview_image_style in Drupal\diff\Plugin\diff\Field\ImageFieldBuilder->build() (line 83 of sites/default/modules/contrib/diff/src/Plugin/diff/Field/ImageFieldBuilder.php).

Drupal\diff\Plugin\diff\Field\ImageFieldBuilder->build(Object) (Line: 94)
Drupal\diff\DiffEntityParser->parseEntity(Object) (Line: 96)
Drupal\diff\DiffEntityComparison->compareRevisions(Object, Object) (Line: 118)
Drupal\diff\Plugin\diff\Layout\UnifiedFieldsDiffLayout->build(Object, Object, Object) (Line: 167)
Drupal\diff\Controller\PluginRevisionController->compareEntityRevisions(Object, Object, Object, 'unified_fields') (Line: 49)
Drupal\diff\Controller\NodeRevisionController->compareNodeRevisions(Object, '82899', '83284', 'unified_fields')
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 574)
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}()
call_user_func_array(Object, Array) (Line: 144)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 64)
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: 99)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 78)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 50)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 656)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

ImageFieldBuilder is looking for the preview image style, but it is not defined.

Proposed resolution

Diff should skip the thumbnail if no preview image style is given.

Workaround

Uncheck "Show image thumbnail"

or better

set preview image style for image.