[IMPROVE] Allow e-mail channel to be used without default department.

[cauefcr]

Proposed changes (including videos or screenshots)

Due to a missing condition in the e-mail input processing, Rocket.Chat was unable to receive e-mails from e-mail channels that did not have a default department.

Issue(s)

The following error is raised when an email message is sent to an email account without default department

W20211206-13:46:39.202(-3)? (STDERR) === UnHandledPromiseRejection ===
W20211206-13:46:39.204(-3)? (STDERR) errorClass [Error]: Provided department does not exists [invalid-department]
W20211206-13:46:39.204(-3)? (STDERR) at Object.setDepartmentForGuest (app/livechat/server/lib/Livechat.js:332:10)
W20211206-13:46:39.204(-3)? (STDERR) at getGuestByEmail (server/features/EmailInbox/EmailInbox_Incoming.ts:46:13)
W20211206-13:46:39.204(-3)? (STDERR) at server/features/EmailInbox/EmailInbox_Incoming.ts:134:16
W20211206-13:46:39.204(-3)? (STDERR) at /Users/renatobecker/.meteor/packages/promise/.0.11.2.q9g02k.d69vo++os+web.browser+web.browser.legacy+web.cordova/npm/node_modules/meteor-promise/fiber_pool.js:43:40 {
W20211206-13:46:39.204(-3)? (STDERR) isClientSafe: true,
W20211206-13:46:39.204(-3)? (STDERR) error: 'invalid-department',
W20211206-13:46:39.205(-3)? (STDERR) reason: 'Provided department does not exists',
W20211206-13:46:39.205(-3)? (STDERR) details: { method: 'setDepartmentForGuest' },
W20211206-13:46:39.205(-3)? (STDERR) errorType: 'Meteor.Error'
W20211206-13:46:39.205(-3)? (STDERR) }
W20211206-13:46:39.205(-3)? (STDERR) ---------------------------------
W20211206-13:46:39.205(-3)? (STDERR) Errors like this can cause oplog processing errors.
W20211206-13:46:39.205(-3)? (STDERR) Setting EXIT_UNHANDLEDPROMISEREJECTION will cause the process to exit allowing your service to automatically restart the process
W20211206-13:46:39.205(-3)? (STDERR) Future node.js versions will automatically exit the process
W20211206-13:46:39.205(-3)? (STDERR) =================================

Steps to test or reproduce

By creating an e-mail channel and not giving it a default department the above error would occur, dropping e-mail messages from Rocket.Chat, with only a console log for an error.

Further comments

[murtaza98]

@cauefcr I found an edge case with your implementation where if the email was first connected to a department, let's say sales, and then a room was closed within this department - Post this, the email was then unassigned from any department on Rocket.Chat, and if the same chat arrives back, ideally I think we shouldn't associate this new chat to the sales department since there is no department connected to the email - but in your implementation, it was still associating it to the Sales department.

Hopefully, this PR should fix this - #23950

[cauefcr]

Thanks for the PR! I didn't test this edge case.

The requested changes were merged