絶対エラーでるSK

on first join:
    set {%player%_level} to 0
    set {%player%_xp} to 0
    set {%player%_next} to 36
on death:
    if attacker is player:
        if victim is zombie:
            if name of victim is "&a&l草原&2のなりすまし":
                message "&a+4 Xp レベル:%{%player%_level}%"
                if {%player%_level} > {%player%_next}:
                    set {%player%_level} to {%player%_level} + 1
                    set {%player%_xp} to {%player%_xp} - {%player%_next}
                    set {%player%_next} to {%player%_next} + 9
                    message "&aLEVELUP! レベル:%{%player%_level}%"