Handle null titled posts

Sometimes posts can have no title. Really old blogs have these since platforms were not smart enough to stop such idiocies from happening. When trying to migrate, we're going to end up throwing up a whole set of mess since hexo (rightly so, always expects a title and cries like a baby when there's none).

This should make things a bit more sane. Tried it out with my blog and it worked. Not sure if rest of the stuff (date, categories, description) need to be worked upon as well.