Guard sync route registration against missing table

Adds a db_version check before registering the collaboration REST
routes so sites that haven't run the upgrade routine yet don't hit
a fatal error from the missing sync_updates table.

Author: josephfusco

src/wp-includes/rest-api.php

@@ -430,7 +430,7 @@ function create_initial_rest_routes() {
 	$icons_controller->register_routes();
 
 	// Collaboration.
-	if ( get_option( 'wp_enable_real_time_collaboration' ) ) {
+	if ( get_option( 'wp_enable_real_time_collaboration' ) && get_option( 'db_version' ) >= 61697 ) {
 		$sync_storage = new WP_Sync_Table_Storage();
 
 		/**