I've just been going through the same hell.
What do you mean you won't know your income next year? I'm assuming that any money you have will either be from your parents, the bursary itself, or possibly part-time work which it specifically states you shouldn't include if you are a full-time student. Unless you happen to own any property or something like that then yes you leave it all blank.
By the way, when you get to the bit about your parents income they want info from the financial year 2015-2016 which hasn't finished yet, so you can't actually apply yet. Idk why they've bothered opening applications this early.