Oi, sorry to keep pestering you dude! `[1,2,3].slice(1,1) == []`. I think what we want to do here is this:
```javascript
if (~i) {
  user.invitations.guilds.splice(i,1); // splice does "destructive set" to array, and returns the removed objects
  User.set('invitations.guilds', user.invitations.guilds);
}
```