REST API: Check if get_blog_details() is callable (#718)

* REST API: Check if get_blog_details() is callable

Author: t-hamano

mu-plugins/rest-api/index.php

@@ -21,10 +21,10 @@ function initialize_rest_endpoints() {
 	$users_controller->register_routes();
 
 	// The Site Quality controller is only needed on the main site. Note: domain check is due to this plugin running on multiple networks.
-	if ( 1 === get_current_blog_id() && 'wordpress.org' === get_blog_details()->domain ) {
+	if ( 1 === get_current_blog_id() && function_exists( 'get_blog_details' ) && 'wordpress.org' === get_blog_details()->domain ) {
 		require_once __DIR__ . '/endpoints/class-wporg-site-quality-controller.php';
 	}
-	
+
 	if ( defined( 'WPORG_THEME_DIRECTORY_BLOGID' ) && WPORG_THEME_DIRECTORY_BLOGID === get_current_blog_id() ) {
 		require_once __DIR__ . '/endpoints/class-wporg-base-locale-banner-controller.php';
 		require_once __DIR__ . '/endpoints/class-wporg-themes-locale-banner-controller.php';