PHPMailer\PHPMailer\Exception: Invalid address:  (to):  in /var/www/html/wp-includes/PHPMailer/PHPMailer.php:1100
Stack trace:
#0 /var/www/html/wp-includes/PHPMailer/PHPMailer.php(1020): PHPMailer\PHPMailer\PHPMailer->addOrEnqueueAnAddress()
#1 /var/www/html/wp-content/themes/UCPB-child/email/email-notification.php(47): PHPMailer\PHPMailer\PHPMailer->addAddress()
#2 /var/www/html/wp-includes/template-loader.php(106): include('...')
#3 /var/www/html/wp-blog-header.php(19): require_once('...')
#4 /var/www/html/index.php(17): require('...')
#5 {main}