Expiration States with Atoa acbs: error

Code:
#===============================================================================



# ** States : Expiration States

#===============================================================================



#-------------------------------------------------------------------------------

# * SDK Log

#-------------------------------------------------------------------------------

#if Object.const_defined?(:SDK)

#  SDK.log('States.ExpirationStates', 'Kain Nobel ©', 4.0, '2013.01.02')

#end



#===============================================================================

# ** RPG::State

#===============================================================================



class RPG::State

  #-----------------------------------------------------------------------------

  # * Expiration

  #-----------------------------------------------------------------------------

  Expiration = {}

  Expiration[25] = 26 # Doom 3 to Doom 2

  Expiration[26] = 27 # Doom 2 to Doom 1

  Expiration[27] = 1  # Doom 1 to Death

  #-----------------------------------------------------------------------------

  # * Expiration Default (*Don't touch*)

  #-----------------------------------------------------------------------------

  Expiration.default = []

  #-----------------------------------------------------------------------------

  # * Experation States

  #-----------------------------------------------------------------------------

  def expiration_states

    # If expiration states nil

    if @expiration_states.nil?

      # Get expiration states setting

      @expiration_states = Expiration[@id]

      # Convert to value to array if integer

      @expiration_states = [@expiration_states] if @expiration_states.is_a?(Integer)

      # If value isn't set as array, return an empty array

      @expiration_states = [] unless @expiration_states.is_a?(Array)

    end

    # Return expiration states

    @expiration_states

  end

end



#===============================================================================

# ** Game_Battler

#===============================================================================



class Game_Battler

  #-----------------------------------------------------------------------------

  # * Alias Listings

  #-----------------------------------------------------------------------------

  alias_method :expirestates_gmbattler_removestate,       :remove_state

  alias_method :expirestates_gmbattler_removestatesauto,  :remove_states_auto

  #-----------------------------------------------------------------------------

  # * Remove States Auto

  #-----------------------------------------------------------------------------

  def remove_states_auto

    # Enable flag to check for expiration states

    @check_expiration_states = true

    # The usual

    expirestates_gmbattler_removestatesauto

    # Disable flag to check for expiration states

    @check_expiration_states = nil

  end

  #-----------------------------------------------------------------------------

  # * Remove State

  #-----------------------------------------------------------------------------

  def remove_state(state_id, force = false)

    # Check if state already inflicted

    state_inflicted = state?(state_id)

    # The usual

    expirestates_gmbattler_removestate(state_id, force)

    # End method if state invalid

    return unless state_id > 0

    # End method if state still exists

    return if state?(state_id)

    # End method unless checking expiration states

    return unless @check_expiration_states

    # End method unless state was previously inflicted before removal

    return unless state_inflicted

    # Get state object

    state = $data_states[state_id]

    # End method if expiration states empty

    return if state.expiration_states.empty?

    # Force the addition of each expiration state

    state.expiration_states.each {|i| self.add_state(i)}

  end

end