Make the default value for date time a less strict about invalid dates.

src/Plugin/WebformHandler/FormProcessorWebformHandler.php

@@ -330,7 +330,11 @@ class FormProcessorWebformHandler extends WebformHandlerBase {
         $element =& WebformElementHelper::getElement($form, $key);
         if ($element) {
           if ($element['#type'] == 'datetime') {
-            $element['#default_value'] = DrupalDateTime::createFromFormat(\DateTime::ATOM, $value);
+            try {
+              $element['#default_value'] = DrupalDateTime::createFromFormat(\DateTime::ATOM, $value);
+            } catch (\InvalidArgumentException $ex) {
+              // is it something else than a date ignore
+            }
           }
           else {
             $element['#default_value'] = $value;