Fall to dead causes server crash

Hi all,

Im working on a zombie mod with saving. Everything loads and saves perfectly. However, if I fall to dead (jump from a too high object) the server crashes and says my values are undefined. I can kill, get killed, do suicide, the mod works perfectly. But when I fall to dead it says thats it undefined. And not 1 thing, but all.

PHP Code:

---

checkachievements()
{
    if(self.rank >= 1 && self.rank5ach==0 )
    {
        text=&"BEGINNER";
        self thread add_achievement(text);
        self.rank5ach=1;
    }

    if(self.rank >= 20 && self.rank20ach==0 )
    {
        text=&"ZOMBIDICAL MANIAC";
        self thread add_achievement(text);
        self.rank20ach=1;
    }
} 


---

I got a hud that shows the correct rank. I also get the message when I get the achievement. It's called from Callback_Playerkilled();
But when I fall to death, it says

Code:

---

pair 'undefined' and '1' has unmatching types 'undefined' and 'int'

---

But it works because I got the message when I reach rank 1. Who can help me?

When falling to death the attacker or eAttacker is the string "world" and not an entity.
If you call checkachievements() on attacker self.rank is undefined.