I should of been more clear ?
The current beta (beta.5) seems to have this issue, which is what you currently get when you run
composer create-project flarum/flarum . --stability=beta
So, if a issue has been reported to be fixed as sijad indicated, the next step would be to see if the fix worked in a forum using the latest code. You can trial this on a local dev-master install or if that is not feasible, with Devflarum which runs the most recent developmental code.
In a metaphorical sense, if you're running code at point E, the error was fixed at point G, installing E and reporting it still occurring after it's been reported fixed doesn't make sense. But if you test a dev-install at point n and the error no longer occurs, you know you've been heard and the issue resolved. The course of action at that point is to wait until the next beta arrives carrying the fix or manually apply the fix yourself (which involves risk). If you trial the latest code and it still doesn't work, then mention the commit versions you were using when reporting it still exists.
Trace
From what I understand, discuss.flarum.org runs later (and possibly some custom) code but not the latest. IMO, you don't want the support forum for a forum software running the latest code of itself ? As for quoting here on discuss, it's not working atm for me either.