fix unicode error on json_decode

Currently have the check a error for unicode-files, there use unicode strings.
As Example the screenshot from a error message. But with unicode-files is it not helpful, necassery to convert strings in entities.

![json-error](https://f.cloud.github.com/assets/133425/2499485/3886d79c-b357-11e3-8159-6306dbc48d2f.png)

Thanks.