I've just gone through it, it looks like it's an error in Construct 2's export.
The error is caused probably when you have a family with one object in it.
If you have a family with one object in it, add a dummy object to the family and re-export it. Let me know if this works for you all!
This is a bug that will be fixed in the next release as well.
Also just to say again don't worry if you can't upload, we will still let you enter, but for now try this family fix.