fix: options in migrate

packages/svelte/src/compiler/migrate/index.js

@@ -149,7 +149,8 @@ export function migrate(source, { filename, use_ts } = {}) {
 			css: 'css' in parsed_options ? () => parsed_options.css ?? 'external' : () => 'external',
 			runes: 'runes' in parsed_options ? () => parsed_options.runes : () => undefined,
 			experimental: {
-				async: true
+				async: true,
+				customRenderer: () => undefined
 			}
 		};