Forum leaderboard 'how does this work' button is broken

On this page Manjaro Linux Forum the ‘How does this work?’ button in the top right does not work.

This is from the console

Uncaught TypeError: this.last is null
    lastNode runtime.js:916
    lastNode runtime.js:916
    lastNode runtime.js:4347
    lastNode runtime.js:1008
    evaluate runtime.js:4424
    _execute runtime.js:4306
    execute runtime.js:4291
    rerender runtime.js:4606
    Ember 2
    Mt runtime.js:4139
    Ember 3
    invoke queue.ts:201
    flush queue.ts:98
    flush deferred-action-queues.ts:75
    _end index.ts:616
    end index.ts:298
    _run index.ts:667
    _join index.ts:640
    join index.ts:362
    Ember 2

Sorry if this isn’t the right place for this. Wasn’t really sure where to put this.