Finding an empty slot in array and using it (Squirrel)

Finding an empty slot in array and using it (Squirrel)

So I have a problem that I have been messing with for a while in Squirrel.
I want to create something that goes through everything inside an array,
e.g:
local array = [1, 2, 3, -1, 5, -1, 7, -1];
and look for those that are -1, I want to use just one of them, the one
that comes up first (which in this case is between 3 and 5).
In my script, when someone destroys a certain object, it sets that objects
id to -1 instead of a regular number, because otherwise it will just
through out errors when trying to use that object. Don't really know if
I'm doing a good job explaining this.
Another example is when players connect to a certain game server, so we
have players with id 0, 1, 3 and 4 connected, so when next player connects
they get the id 2. That is the thing i'm after with the arrays.
I have tried several things, only thing that is closest to it is this:
for(local i=1; i < Array.len(); i++){
if(Array[i].id != -1){
count++;
} else {
count = i;
}
}
But the problem with this one is that it only takes the last ID and
replaces it, so we have objects 0, 1, 2 and 3 If I would destroy 3 and
create a new one, no problem. If I would destroy either 0, 1 or 2 instead
and create a new one it would not take that slot, but instead go for
number 4, which then does not work.
Thanks for reading, hopefully anyone out there can help me with this.