Fix notices in API.

Author: mauteri

includes/core/classes/class-event-rest-api.php

@@ -507,8 +507,8 @@ public function update_rsvp( WP_REST_Request $request ): WP_REST_Response {
 		$user_id         = isset( $params['user_id'] ) ? intval( $params['user_id'] ) : $current_user_id;
 		$post_id         = intval( $params['post_id'] );
 		$status          = sanitize_key( $params['status'] );
-		$guests          = intval( $params['guests'] );
-		$anonymous       = intval( $params['anonymous'] );
+		$guests          = intval( $params['guests'] ?? 0 );
+		$anonymous       = intval( $params['anonymous'] ?? 0 );
 		$event           = new Event( $post_id );
 
 		// If managing user is adding someone to an event.