poller wait() code example does not delete() on earlier ? error return.

[YpeKingma]

For safety poller.add() requires:

The source must be delete()d from this Poller before it is dropped.

And the wait() example code has:

unsafe {
    poller.add(&socket, Event::all(key))?;
}

let mut events = Events::new();
let n = poller.wait(&mut events, Some(Duration::from_secs(1)))?;
poller.delete(&socket)?;

The ? at the wait() call may cause an Error return without delete() being called.

Is this example safe?