Occasional 500 TypeErrors on some links throughout

[skilfullycurled]

Hi again. Sorry to be filling up the issue box lately. There are 500 TypeErrors on some of the pages, and they occur every time that page is requested. They're expressed (no web framework pun intended) all the way back to page 28. Here are two examples, notated as page:image where the image number is from 1-12 left to right, top to bottom.

1:10- http://infragram.org/i/53e82a8f0ab503231b000c1e
28:6 - http://infragram.org/i/52ed7f8a836488e24a000016