Fix contact ID

Civi/StripeImport/Charge.php

@@ -38,6 +38,10 @@ class Charge extends Base {
     return $this->contactID;
   }
 
+  public function hasContactID(): bool {
+    return isset($this->contactID);
+  }
+
   /**
    * @var int The CiviCRM Contribution ID
    */
@@ -104,7 +108,7 @@ class Charge extends Base {
       $this->setDescription('Stripe: Manual import via API');
     }
 
-    if (empty($this->getContactID())) {
+    if (!$this->hasContactID()) {
       // Derive contact ID from stripe customer
       if (empty(\CRM_Stripe_Api::getObjectParam('customer_id', $stripeCharge))) {
         throw new \Exception('Missing customer_id in Stripe Charge. Cannot derive contact ID');