Fix access violation in Handler

[Xoffio]

This fixes an access violation when Handler has any fields. For example:

If someone declares fields to Handler like:

struct Handler {
    memory_access_list: Arc<Mutex<Vec<(String, HitData)>>>,
}

That used to crash before the fix.

[s1341]

I don't quite follow your fix. Can you explain it to me?

Also a test would be great!

[Xoffio]

I'm going to close this. This was fixed on #239