edx/edx-platform — pull request #2058 by waheedahmed (2013-12-31 12:27:46+00:00)
Title: JSON serialization error fixed.

ORA-195
An empty string is passing to _parse_score_msg function when post_assessment key is not found in dict which causes an exception of JSON serialization.

Fixed this by giving default value to get function an empty dict as a string e.g.("{}").