Not a very common thing, full of rare edge conditions, but the least I could do is file a bug report.
Repro on tests-passed
Create a topic
Unlist it
Set topic timer to schedule publishing to a category somewhere in the future.
When other users are viewing that topic - before it is actually published - and they do not have access to the future category, the code that says “This topic will be published to #category in x days.” will crash (because it cannot access the slug of the future category) and cause eternal reloading of the page.
Yes, it’s a very rare thing to publish a topic to a more restricted category while users do have access to the unlisted topic.
I wanted to confirm I’m seeing this behavior as well.
Followed the reproduction steps as described, and then viewed the topic as a user who didn’t have permission to access the category that the topic was set to publish to.
The title of the topic gets displayed over and over again every few seconds until the page is closed.
Without the timer set to publish the topic to a category that the user doesn’t have access to, the topic is displayed as normal (still unlisted).
Discourse Version 2.9.0.beta3
I would expect in this situation that the topic would either be displayed as a typical unlisted topic in the original category that the topic was created in (until the topic is scheduled to publish), or that there would be a message stating that the user doesn’t have permission to access that category of topic.
Certainly a rare edge case, but nonetheless hopefully this information helps resolve this bug.