Help Needed! Cannot read property 'top' of undefined in Production only

[sayling]

Hey guys!

First of all, how awesome is this theme?
I've taken this theme and got it working on Ruby-on-Rails. Well, kind of.

It runs 90% OK locally, aside from a few weird quirks that make it different from the original. I'll work on those later.

However, my Ruby app is now running on Heroku - and in in this environment only, I get these errors in console:
Cannot read property 'top' of undefined

Additional to this, the cards are un-clickable and the background pattern disappears!

Now I have a suspicion the deployment has broken the way my assets are saved (as ruby smooshes all the assets into one 'manifest' file), but I'm hideously bad at JS and I confess I've mostly shoe-horned the code into my app without trying to read it too much. So I'm not sure if it's my filesystem, or a reference to a 3rd party thing or what.

If anyone's really familiar with the codebase and can tell me if it's because vars from other files are missing, or something similar, I will know where to head to fix!

Code is hosted here: http://sampetersnet.herokuapp.com/blog
(Note, there are other JS errors here too...)

If I can give any more info let me know, I'll do my best.

Thanks in advance!