Yep, that little single-block platform isn't meant to be there. A friend of mine found it, as well. I've fixed that for an eventual future patch. The problem is that single tiles in a couple of the tilesets end up being completely black, and that makes it fairly easy to miss when you're roughly scribbling in an environment like I did in that area. Easy way to check for them in the current version of the editor is to switch to another tileset, then back again.
