refac/security: set ac to private by default

src/lib/components/workspace/common/AccessControl.svelte

@@ -13,7 +13,7 @@
 	export let onChange: Function = () => {};
 
 	export let accessRoles = ['read'];
-	export let accessControl = null;
+	export let accessControl = {};
 
 	export let allowPublic = true;