Omnichannel Departments and offline behaviour

Description:

When no Agents are online, an offline form is presented to the user to leave a message. However, if no Agents are online for a specific department, the chat is initialized without any problems but when sending a message a "no-agent-online" error is shown.

Steps to reproduce:

1. Add an Agent to a Department "Test".
2. Have the agent online.
3. Register the User with the following code:

  RocketChat(function() {
    this.registerGuest({
      name: 'visitor Name',
      email: 'sample@rocket.chat',
      department: 'Another'
    });
  });

4. Test the Livechat and type anything. An error should be thrown.
5. Extra step: have the Agent go offline. You will see the offline form now.

Expected behavior:

If there are no online agents for the current department, the offline form (or whatever offline behaviour that was set) should be shown. It should be exactly the same as what happens when all agents are offline.

Actual behavior:

A "no-agent-online" error is shown in the chat widget.

Server Setup Information:

• Version of Rocket.Chat Server: 3.6.2
• Operating System: Ubuntu 20.04
• Deployment Method: snap
• Number of Running Instances: 1
• DB Replicaset Oplog:
• NodeJS Version:
• MongoDB Version:

Client Setup Information

• Desktop App or Browser Version: Desktop
• Operating System: Ubuntu 18.04

Reproduce the department-specific case using the registerGuest snippet and compare it with the all-agents-offline behavior in the livechat widget. The work is complete when a department with no online agents shows the configured offline behavior instead of a no-agent-online error.