In cbox-polyfill for get_site_template_id(), ensure that saved option…

…s are returned as integers.

Otherwise strict comparisons will fail later. In this case, it was causing an extra
instance of the fallback site ID to be appended to the Site Templates > Group Type Templates
panel in some cases.

See #3227.

wp-content/themes/openlab/lib/cbox-polyfills/class-cbox-group-type.php

@@ -30,6 +30,7 @@ public function get_label() {
 	 */
 	public function get_site_template_id() {
 		$site_template_ids = get_option( 'openlab_group_type_default_site_template_ids' );
+		$site_template_ids = array_map( 'intval', $site_template_ids );
 
 		$saved_site_template_is_valid = false;