Case where post_id=0 in DB

Hi

I have find a bug which occurs when we swap from using the reorder capability for a category to not using it (the yes/no radio button), and back again.

When cancelling the reordering by checking “No”, there’s a post request sent with a bunch of “,,,,,,” as the post list payload, which create lines in the table with a post_id value of 0

Then we have a bunch of empty lines in the reorder page.

I can fix it, feel free to reply for giving me direction to create a pull request.