refs #42288, fixes participant save priceset php 8 compatibility.

Author: jimyhuang

CRM/Event/Form/Participant.php

@@ -1460,8 +1460,8 @@ public function postProcess() {
     }
 
     // also store lineitem stuff here
-    if (($this->_lineItem & $this->_action & CRM_Core_Action::ADD) ||
-      ($this->_lineItem && CRM_Core_Action::UPDATE && !$this->_paymentId)
+    if ((!empty($this->_lineItem) && ($this->_action & CRM_Core_Action::ADD)) ||
+      (!empty($this->_lineItem) && ($this->_action & CRM_Core_Action::UPDATE) && !$this->_paymentId)
     ) {
       require_once 'CRM/Price/BAO/LineItem.php';
       foreach ($this->_contactIds as $num => $contactID) {