fix: fall back to subdomain for blogname when title is empty on duplication

When $args->title arrives empty (e.g. via WooCommerce checkout flow),
the duplicated site kept the template's blogname instead of the
customer's site name. Now falls back to the subdomain portion of the
site's domain, ensuring the blogname always reflects the new site.

Author: superdav42

inc/helpers/class-site-duplicator.php

@@ -323,9 +323,14 @@ protected static function process_duplication($args) {
 
 		// Ensure the requested title is applied after duplication, since the
 		// table copy may overwrite the blogname option set during site creation.
-		if (! empty($args->title)) {
-			update_blog_option($args->to_site_id, 'blogname', $args->title);
-		}
+		// When no title was provided (e.g. WooCommerce checkout flow), fall back
+		// to the subdomain portion of the site's domain so the duplicated site
+		// doesn't keep the template's blogname.
+		$new_title = ! empty($args->title)
+			? $args->title
+			: preg_replace('/\..*$/', '', $args->domain);
+
+		update_blog_option($args->to_site_id, 'blogname', $new_title);
 
 		/**
 		 * Allow developers to hook after a site duplication happens.