defend against undefined plan_code

services/web/app/coffee/Features/Subscription/SubscriptionController.coffee

@@ -170,6 +170,10 @@ module.exports = SubscriptionController =
 		AuthenticationController.getLoggedInUser req, (error, user) ->
 			return next(error) if error?
 			planCode = req.body.plan_code
+			if !planCode?
+				err = new Error('plan_code not defined')
+				logger.err {user_id: user._id, err}, "error updating subscription"
+				return next(err)
 			logger.log planCode: planCode, user_id:user._id, "updating subscription"
 			SubscriptionHandler.updateSubscription user, planCode, null, (err)->
 				if err?