added logging and default calback

services/web/app/coffee/Features/Notifications/NotificationsBuilder.coffee

@@ -5,7 +5,7 @@ module.exports =
 
 	groupPlan: (user, licence)->
 		key : "join-sub-#{licence.subscription_id}"
-
+		logger.log user_id:user_id, key:key, "creating notification key for user"
 		create: (callback = ->)->
 			messageOpts = 
 				groupName: licence.name

services/web/app/coffee/Features/User/UserHandler.coffee

@@ -6,7 +6,7 @@ logger = require("logger-sharelatex")
 
 module.exports = UserHandler =
 
-	populateGroupLicenceInvite: (user, callback)->
+	populateGroupLicenceInvite: (user, callback = ->)->
 		logger.log user_id:user._id, "populating any potential group licence invites"
 		licence = SubscriptionDomainHandler.getLicenceUserCanJoin user
 		if !licence?