What's about this Multilanguage add-on? The error says there is a undefinied method in the Entity of this add-on.
The getStructure() method is for the database. So it seems to be a problem with this add-on. Try to disable it and take a look.
I check all directories for entities. This add-on has such a directory but WITHOUT the corresponding things that the add-on expects! I have therefore built in a more precise check of the data found. Sorry and Thanks