Index: branches/5.2.x/units/orders/orders_event_handler.php
===================================================================
--- branches/5.2.x/units/orders/orders_event_handler.php
+++ branches/5.2.x/units/orders/orders_event_handler.php
@@ -2219,7 +2219,10 @@
 
 					$shipping_email = $object->GetDBField('ShippingEmail');
 					$email_params['to_email'] = $shipping_email ? $shipping_email : $email_params['_user_email'];
-					$this->Application->emailUser('ORDER.SHIP', null, $email_params);
+
+					if ( strlen($email_params['to_email']) ) {
+						$this->Application->emailUser('ORDER.SHIP', null, $email_params);
+					}
 
 					// inform payment gateway that order was shipped
 					$gw_data = $object->getGatewayData();