[Bug] CAS Log in / Authenticate is not possible with some browsers

Hello,

Description:

With CAS authentication, the actual way to log in prevent access with some broswers (tested with Jelly Browser).

The Log in button is stuck with its loading icon forever (like image in step 5 of https://github.com/RocketChat/Rocket.Chat/issues/7071).

This is the case if CAS session :

• doesn't exists and user open one in other window (because pop up don't fire).
• already exists (opened previously).

I've also tested a fallback solution : using direct URL of the log in pop up.
The URL is something like that : your-cas/cas/login?service=your-rocket/tocken
But it seems the tocken is necessary but not reusable, so this solution doesn't permit acces neither.

Steps to reproduce:

Expected behavior:

• No pop up for authenticate (what about using same window ?)
  Or
• If CAS session is already open, direct access, without need to click on a button (also pointed in https://github.com/RocketChat/Rocket.Chat/issues/8050).

Actual behavior:

see "description".

Server Setup Information:

Version of Rocket.Chat Server: 3.9.x
Operating System: Linux

No source file or test is named. Start by reproducing CAS authentication in the affected browser with both an existing and a newly opened CAS session, then trace the login popup and token flow; done means authentication completes without a stuck loading state in both cases.