Steps to replicate the issue (include links if applicable):

• Create an event that has a chat link
• Wait for the event to end (or set its end date to the past after you've created it)
• Visit the event page as someone who is NOT an organizer or participant of the event (logged-out works, too)
• Click "More details" to open the info dialog

What happens?:
There's an empty "Join event chat group" section with no content in it.

What should have happened instead?:
The "Join event chat group" section should be hidden.

Other information (browser name/version, screenshots, etc.):

• Reproducible on meta: https://meta.wikimedia.org/wiki/Event:International_Youth_Day_2023
• For context, when the event is still open we display the following message when a non-participant opens the dialog: «Register to view the chat group link.». But if the event has ended, you can no longer register. I don't think it would be useful to have a separate error message for this scenario (to explain that the event has a chat link, but there's no way for people to see it).
• The same thing happens not just when an event has ended, but also when the registration is closed, or if the user is blocked.
• The same bug also affects the meeting link section, under the same conditions, and that also has a message asking users to register. I'm not sure if we need a separate task for that.