Rpg Maker Developers Group

Hi!

As the title says i'm trying to make a shop where the player can sell actors. At the moment i'm just working on the eventing side and i'm a bit stuck so thought id check to see if i could get any pointers. I'm aware what i might have already could be a bit of an odd setup. So any way to improve the system would be great too

How i want it to work
When you interact with the shop the player has the option to sell their actors for money. I want to be able to scroll through your actors and choose which ones you want to sell. This is what i have so far if you can view the gif below.

https://drive.google.com/open?id=0B6j4W9Odp86nRlU2Rk1DSHdwRnM

The issue
So it seems work fine until i start selling actors that are at the end of the party list then i get this error. I cant quite figure out why?
If i sell actors in this order 1,2,3,4 it works. but if i sell actors in this order 4,3,2,1 then i get this error.


Im pretty new to RPG maker MV and using any JavaScript so any help would be greatly appreciated!
Here is all the eventing i have set up for the shop so far. Apologies its fairly long because it has 3 conditional branches in there that do pretty much the same thing but stop the player from being able to go to the next/previous actor if they dont exist.
Hopefully some of this makes sense.. if not willing to go into further detail

Thanks!! )