[BUG][API] channel.members is returning error for GENERAL room

[rafaelks]

Description:

API is returning error, but works for other rooms.

Server Setup Information:

• Version of Rocket.Chat Server: 0.60.0-develop

Expected behavior:

• Should return the members list;

Actual behavior:

:method: GET
:scheme: https
:path: /api/v1/channels.members?roomId=GENERAL&count=50&offset=0
:authority: foo.rocket.chat
accept: */*
content-type: application/json
x-auth-token: foobar
user-agent: Rocket.Chat/127 CFNetwork/893.14 Darwin/17.3.0
x-user-id: Xx6KW6XQsFkmDPGdE
accept-language: en-us
accept-encoding: br, gzip, deflate

:status: 400
access-control-allow-origin: *
cache-control: no-store
content-encoding: gzip
content-type: application/json
date: Fri, 08 Dec 2017 19:59:48 GMT
pragma: no-cache
vary: Accept-Encoding
x-instance-id: xSRJaNFk2Gt2tTbmr
content-length: 91

{
  "success": false,
  "error": "Cannot convert undefined or null to object"
}