adding <none> to link field when entity does not exist anymore

core/modules/link/src/Plugin/Field/FieldWidget/LinkWidget.php

@@ -76,8 +76,13 @@ protected static function getUriAsDisplayableString($uri) {
       // Show the 'entity:' URI as the entity autocomplete would.
       // @todo Support entity types other than 'node'. Will be fixed in
       //   https://www.drupal.org/node/2423093.
-      if ($entity_type == 'node' && $entity = \Drupal::entityTypeManager()->getStorage($entity_type)->load($entity_id)) {
-        $displayable_string = EntityAutocomplete::getEntityLabels([$entity]);
+      if ($entity_type == 'node') {
+        if ($entity = \Drupal::entityTypeManager()->getStorage($entity_type)->load($entity_id)) {
+          $displayable_string = EntityAutocomplete::getEntityLabels([$entity]);
+        }
+        else {
+          $displayable_string = '<none>';
+        }
       }
     }
     elseif ($scheme === 'route') {