worldborder following animal skript

[Exotic_pink]

yo i got the skript from 

 and changed it a little bit, it dosent look like the issue was ever resolved im having the same problem my console says
Console error: [08:31:32 INFO]: ...er center {_x} {_z}<--[HERE]

[Exotic_pink]

function spawnmob(loc: location, entity: entity type):
    spawn {_entity} at {_loc}

on death:
    if victim is pig:
        if victim's name is "&b&lWorld Border":
            cancel event

command /pig:
    permission: op
    permission message: No
    trigger:
        spawnmob(location of player, pig)    
        set name of last spawned entity to "&b&lWorld Border"
        set {_entity} to last spawned entity

every 0.1 seconds in world "world":
    set {_x} to x-position of {_entity}
    set {_z} to z-position of {_entity}
    make console execute command "worldborder center {_x} {_z}"