Insert throws Unhandled error in request

[almstrand]

It is not well documented that documents in the users table must define a groups property. The earlier CLI document (https://github.com/rethinkdb/horizon-docs/pull/106/commits/bcbc1a3de614d9247a223965092d443036ea95da) and several independent sources online suggest adding users like so:

horizon('users').store({id: '4C720BD1-2729-46BA-9213-ED84DEDE3120'});

If a user is added that way, without a groups property, and Horizon is initialized as follows ...

var horizon = Horizon({authType: { token: '...'}});

... the server throws an exception when e.g. attempting to insert a document to a table:

Horizon ready for connections
debug: Handling HTTP request to horizon subpath: horizon.js
debug: Client connection established.
debug: Handling HTTP request to horizon subpath: horizon.js.map
debug: Received handshake: {"request_id":0,"method":"token","token":"eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzUxMiJ9.eyJpZCI6InRtcCIsInByb3ZpZGVyIjpudWxsLCJpYXQiOjE0NzM5OTU5MDIsImV4cCI6MTQ3NDA4MjMwMn0.a6FrjflkIMoommv8wGuilz0UrXtPNV7RuSl_bX_w3GUpyZI2BbQpDzJgk-cC_q0adwOEDgDVgheybzwG8-hlLg"}
debug: Sending response: {"token":"eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzUxMiJ9.eyJpZCI6InRtcCIsInByb3ZpZGVyIjpudWxsLCJpYXQiOjE0NzM5OTU5MDIsImV4cCI6MTQ3NDA4MjMwMn0.a6FrjflkIMoommv8wGuilz0UrXtPNV7RuSl_bX_w3GUpyZI2BbQpDzJgk-cC_q0adwOEDgDVgheybzwG8-hlLg","id":"tmp","provider":null,"request_id":0}
debug: Received request from client: {"request_id":1,"type":"store","options":{"collection":"test","data":[{"id":1}]}}
debug: Unhandled error in request: TypeError: Cannot read property 'Symbol(Symbol.iterator)' of undefined
    at Request.evaluate_rules (/usr/local/lib/node_modules/horizon/node_modules/@horizon/server/src/request.js:20:41)
    at new Request (/usr/local/lib/node_modules/horizon/node_modules/@horizon/server/src/request.js:12:10)
    at Client.handle_request (/usr/local/lib/node_modules/horizon/node_modules/@horizon/server/src/client.js:159:21)
    at /usr/local/lib/node_modules/horizon/node_modules/@horizon/server/src/client.js:107:47
    at Client.error_wrap_socket (/usr/local/lib/node_modules/horizon/node_modules/@horizon/server/src/client.js:50:7)
    at WebSocket.<anonymous> (/usr/local/lib/node_modules/horizon/node_modules/@horizon/server/src/client.js:107:18)
    at emitTwo (events.js:100:13)
    at WebSocket.emit (events.js:185:7)
    at Receiver.ontext (/usr/local/lib/node_modules/horizon/node_modules/ws/lib/WebSocket.js:841:10)
    at /usr/local/lib/node_modules/horizon/node_modules/ws/lib/Receiver.js:536:18
    at /usr/local/lib/node_modules/horizon/node_modules/ws/lib/Receiver.js:368:7
    at /usr/local/lib/node_modules/horizon/node_modules/ws/lib/PerMessageDeflate.js:249:5
    at afterWrite (_stream_writable.js:355:3)
    at onwrite (_stream_writable.js:346:7)
    at WritableState.onwrite (_stream_writable.js:89:5)
    at afterTransform (_stream_transform.js:79:3)
    at TransformState.afterTransform (_stream_transform.js:54:12)
    at Zlib.callback (zlib.js:613:5)
debug: Closing client connection with message: Unhandled error: TypeError: Cannot read property 'Symbol(Symbol.iterator)' of undefined
debug: info: {"request_id":null,"error":"Unhandled error: TypeError: Cannot read property 'Symbol(Symbol.iterator)' of undefined","error_code":0}
debug: Client connection terminated.

It seems the CLI documentation can be improved in this regard, to detail how users can be added to the table after executing hz make-token [user] (https://github.com/rethinkdb/horizon-docs/issues/121) but perhaps this exception should also be avoided in the server code by not iterating over users with no groups defined, or perhaps implicitly assigning the default group?