Mongo Update is returning internal server error

router.get('/addInv', function(req, res, next){
  var usrInv = req.query.invusr;
  EventData.update({_id:"5a6e22140c87a94340ac33ca"}, 
  {$set: 
    {
      invit: usrInv 
    }
  })
});

When I try to insert the array contained within the 'usrInv' variable, the server returns an error! Is there something wrong with the code?