WSOD on preview of event with social_event_addtocal enabled

Problem/Motivation

WSOD when preview

Drupal\Core\Entity\EntityMalformedException: The "node" entity cannot have a URI as it does not have an ID in Drupal\Core\Entity\EntityBase->toUrl() (line 161 of core/lib/Drupal/Core/Entity/EntityBase.php).
Drupal\social_node\Entity\Node->toUrl('canonical', Array) (Line: 155)
Drupal\social_event_addtocal\Plugin\SocialAddToCalendarBase->getEventDescription(Object) (Line: 91)
Drupal\social_event_addtocal\Plugin\SocialAddToCalendarBase->generateSettings(Object) (Line: 27)
Drupal\social_event_addtocal\Plugin\SocialAddToCalendar\AddToOutlook->generateUrl(Object) (Line: 255)
_social_event_addtocal_get_links(Object) (Line: 107)
social_event_addtocal_node_view(Array, Object, Object, 'full')
call_user_func_array(Object, Array) (Line: 426)
Drupal\Core\Extension\ModuleHandler->Drupal\Core\Extension\{closure}(Object, 'social_event_addtocal') (Line: 405)
Drupal\Core\Extension\ModuleHandler->invokeAllWith('node_view', Object) (Line: 433)
Drupal\Core\Extension\ModuleHandler->invokeAll('node_view', Array) (Line: 288)
Drupal\Core\Entity\EntityViewBuilder->buildMultiple(Array) (Line: 239)
Drupal\Core\Entity\EntityViewBuilder->build(Array)
call_user_func_array(Array, Array) (Line: 101)
Drupal\Core\Render\Renderer->doTrustedCallback(Array, Array, 'Render #pre_render callbacks must be methods of a class that implements \Drupal\Core\Security\TrustedCallbackInterface or be an anonymous function. The callback was %s. See https://www.drupal.org/node/2966725', 'exception', 'Drupal\Core\Render\Element\RenderCallbackInterface') (Line: 788)
Drupal\Core\Render\Renderer->doCallback('#pre_render', Array, Array) (Line: 374)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 204)
Drupal\Core\Render\Renderer->render(Array, ) (Line: 242)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 580)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 243)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object, Object) (Line: 132)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object, Object) (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object, 'kernel.view', Object)
call_user_func(Array, Object, 'kernel.view', Object) (Line: 142)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch(Object, 'kernel.view') (Line: 174)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 81)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 54)
Drupal\simple_oauth\HttpMiddleware\BasicAuthSwap->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: 728)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Steps to reproduce

enable social_event_addtocal
create a new event
do not save it
preview it
WSOD with the above error

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes