fix ExternalAccount.findOrRegister

lib/models/external-account.js

@@ -92,7 +92,7 @@ class ExternalAccount {
             return User.createUser('', usernameToBeRegistered, undefined, undefined, undefined, User.STATUS_ACTIVE);
           })
           .then(newUser => {
-            return this.associate(providerType, accountId, newUser._id);
+            return this.associate(providerType, accountId, newUser);
           });
 
       });