Issue #3025039: New non translatable field on translatable content throws error

core/lib/Drupal/Core/Field/WidgetBase.php

@@ -402,6 +402,9 @@ public function extractFormValues(FieldItemListInterface $items, array $form, Fo
 
       // Assign the values and remove the empty ones.
       $widget = NestedArray::getValue($form, $field_state['array_parents']);
+      if (!$widget && isset($form[$field_name])) {
+        $widget = $form[$field_name]["widget"];
+      }
       if (Element::isVisibleElement($widget)) {
         $items->setValue($values);
         $items->filterEmptyItems();