contact id not required

api/v3/Stripe/Importsubscription.php

@@ -74,7 +74,9 @@ function civicrm_api3_stripe_importsubscription($params) {
   $importer = new \Civi\StripeImport\Subscription();
   $importer->setPaymentProcessorID($params['ppid']);
   $importer->setStripeSubscriptionID($params['subscription']);
-  $importer->setContactID($params['contact_id']);
+  if (!empty($params['contact_id'])) {
+    $importer->setContactID($params['contact_id']);
+  }
   if (!empty($params['recur_id'])) {
     $importer->setContributionRecurID($params['recur_id']);
   }