show error msg if content rating info invalid (bug 948524)

The response puts the "No records found." inside the "rows" key. The code thought if there was a "rows" key, there were ratings.

![screen shot 2013-12-13 at 1 22 36 pm](https://f.cloud.github.com/assets/674727/1746354/ac3930c2-643d-11e3-9bbe-181cd0553f4c.png)

Also set a max_length on the security_code.