Did you upgrade both EE and Wygwam? I'm not sure whichI think this should fix you upgraded and to what version.up:
Also did you visit the Wygwam settings page to run the database updates? If not, you'll need to do that.https://getsatisfaction.com/pixelandtonic/topics/undefined_index_config_after_upgrade#reply_10005608
It would be goodYou'll need to know exactly what you upgraded and what process you used for itre-save the Matrix field that contains your Wygwam field.
Thank you!
-Lisa