[fix] mark css/instance/module Ast properties as optional

[metonym]

Description

Parsing a Svelte component with only markup will return undefined for css, instance, and module.

Currently, all properties in the Ast interface are required, which can cause type errors.

svelte/src/compiler/interfaces.ts

Lines 132 to 137 in d1b3f46

	export interface Ast {
	html: TemplateNode;
	css: Style;
	instance: Script;
	module: Script;
	}

Repro

// parser.ts
import { parse } from "svelte/compiler";

const ast = parse("");

console.log(ast.instance.start);

// TypeError: Cannot read properties of undefined (reading 'start')

[Conduitry]

Type fix released in 3.46.4 - thanks!