(N.B. I'm not sure if this patch belongs here.)

Using a buffer with the following contents (JSON), espresso-mode would
break telling me it expected a number or marker but got nil whenever I
tried to indent the region. I put together a patch which effectively
indents it correctly and doesn't report an error. It basically checks
that (char-before) is non-nil before comparing it to ?\).

[
   {
     "pk": 2,
  "fields": {
          "url": "http://abc.go.com/",
       "name": "ABC"
    }
      }
]

Attached is the patch. I'm not sure about the format, but I hope it can be used.

-- 
Deniz Dogan