Clean up get() calls, remove commented out code

@Ignat99 PTAL.

As suggested by @dionyziz at https://github.com/OpenBazaar/OpenBazaar/pull/658#issuecomment-56653243 I created a PR out of my own code-review comments.
If ```contract_body``` isn't a dictionary.  E.g., if it happens to be a string, null or a list.