That error is just showing up in the log, but otherwise everything works? If I remember correctly, that error messages is from getAttrByName() being called for a character sheet attribute that doesn't exist for a token (such as one that doesn't use the character sheet). Unfortunately, there isn't a way to check and see if an attribute exists in the character sheet (ones that are defaulted or that are not yet filled out will not have actual attribute objects yet). So long as it is just in the log, it is not a problem, just log detritus I have no control over. If you're getting a crash though, that's different and I'd be happy to help debug it.