Thanks, this was fixed in BE 188.8.131.52 (after the RC). You can still delete the Page outside of the control panel -- e.g. using the Delete link under the Page when viewing the page on the front end of the website.
You can also fix it too if you'd like so Delete works from the control panel. In the App_Code folder is a Posts.cs file. Line 69 has:
var page = Post.GetPost(new Guid(id));
... that should be ...
var page = Page.GetPage(new Guid(id));