Allow users to recover submitted content on error

[Colonel_mortis]

If there's an error, especially an EX class error, the data submitted by the user ought to be recovered as far as possible, either by not clearing the editor autosave until the page has loaded successfully, or by attempting to recover the contents of the post on the error page.

[TSP]

Yeah, I've mentioned this before. 

Having the autosave lose it's content before it has been successfully confirmed it has been stored in the database is an extremely bad user experience. It shouldn't clear on form submit, it should clear on confirmation that the content has been inserted into the database.