Set timer.active = false before calling end_fn

[pitou]

Hi, I was thinking that maybe setting a timer as inactive before calling end_fn could be more useful; in my case I was calling restart_timer (with start_paused === false) inside end_fn but the timer was not actually restarted because timer.active was being re-setted to false immediately after the callback call. Thank you.

[benwiley4000]

@poetcyborg Sounds good to me! I had originally placed that line after the function call because the logic in my head said that the timer isn't "inactive" until the final callback is invoked. But really, your approach makes more sense and I hadn't considered cases where the end callback would restart the timer.