Attendance confirmation page freezes

[SleepyEntropy]

When confirming attendance of a talk, a loading animation is shown, yet nothing noticeable happens.This also occurs when pressing the decline button, except on the talk page.

Upon refreshing/going back, the talk will display a star next to it on the schedule page, and on the talk page the user's name will be added to the attending list, along with the attend button changing to decline.

(TL;DR: Changes are applied, yet users are just shown a loading animation.)