same or similar problem as CONF-12434, but was asked to create a new issue

one way to reproduce (may be others but this is how i got it):

• start writing a blog post
• allow the post to get auto-saved (see draft saved in upper right corner)
• leave the blog page
• start writing a blog post again in the same space
• there will be a box asking what to do with the draft, choose discard draft
• type something in the post
• go to preview tab
• get error (see screenshot)