Handle JSON parse errors for parsing data-config attribute

Please review this before accepting it, because I do not know of any implications of this change (it could just load the default configuration, or it could blow up).

The HTML for the CKEditor widget is:
\<textarea class="django-ckeditor-textarea" cols="40" data-config-name="default" id="id_content" name="content" rows="10"\>\</textarea\>

The fix for this could be as simple as adding a data-config="\<something\>" attribute to the textarea, but I haven't done enough troubleshooting to figure out if that is a proper fix or not.

I'm not sure if I should include a data-config attribute on the textarea tag or not, but this got the widget loading for me.