script error

#=============================================================================
# Quest Log Screen
#-----------------------------------------------------------------------------
# ** Version 2.3
# ** Original by Sthrattoff
#=============================================================================
# Description :
# This script enables the ability to show current active quest.

# Features :
# EXTREMELY SIMPLIFIED! Now the script is just about 150 lines length including comments.
# Unlimited amount of quest can be added.
# Use variable to mark quest's progress.

# Limitation :
# Only can store up to 12 progresses per quest.

# History :
# Version 1.0 : Initial release.
# Version 1.2 : Add "Types" features.
# Version 2.0 : Changes in programming style and infinite quest support.
# Version 2.2 : Cut the script length to about 150 lines.
# Version 2.3 : Add "Quest Progress" bar in exchange of "Types" removal.

# Instruction
# Just put this script above main.

# Configuration :
# To add a quest, fill these information by using .push
# $names.push "Name"
# $types.push "Type"
# $description.push (["line1", "line2", ..., "Line5"])
# $objectives.push (["onjective1", ..., "objective12"])
# $var_ID.push ID_NUMBER
# $end_val.push END_VALUE

# Credits
# See the header + Blizzard and Enterbrain
#=============================================================================
class Scene_Quest
 
  # Defines array variables
    $names = []
    $description = []
    $objectives = []
    $var_ID = []
    $end_val = []
 
  # The main process
  def main
    @quest_list = Window_Command.new(160, $names)
    @quest_window = Window_Quest.new
    @quest_window.x = 160
    Graphics.transition
    loop do
      Graphics.update
      Input.update
      update
      break if $scene != self
    end
    Graphics.freeze
    @quest_list.dispose
    @quest_window.dispose
  end
 
  def update
    @quest_list.update
    @quest_window.update
    if @quest_list.active
      update_quest
      return
    end
  end
 
  def update_quest
    if Input.trigger?(Input::B)
      $game_system.se_play($data_system.cancel_se)
      $scene = Scene_Map.new
      return
    end
    $id = @quest_list.index
    return
  end
 
end   

class Window_Quest < Window_Base
 
  def initialize
    super(0, 0, 480, 480)
    self.contents = Bitmap.new(width - 32, height - 32)
    refresh
  end
 
  def refresh
    self.contents.clear
    self.contents.font.color = system_color
    self.contents.draw_text(0, 0, self.width - 32, 32, $names[$id.to_i].to_s, 1)
    self.contents.draw_text(0, 192, self.width - 32, 32, "Tugas", 1)
    self.contents.draw_text(0, 416, self.width - 32, 32, "Proses")
    self.contents.font.color = normal_color
    for i in 0..4
      self.contents.draw_text(0, i * 32 + 32, self.width - 32, 32, $description[$id.to_i][i].to_s)
    end
    a = b = $game_variables[$var_ID[$id.to_i]]
    if a > 5
      self.contents.draw_text(240, (a - 6) * 32 + 224, 240, 32, "• " + $objectives[$id.to_i][a].to_s)
    else
      self.contents.draw_text(0, a * 32 + 224, 240, 32, "• " + $objectives[$id.to_i][a].to_s)
    end
    self.contents.font.color = disabled_color
    if b > 0
      for j in 0..(b - 1)
        if j > 5
          self.contents.draw_text(240, (j - 6) * 32 + 224, 240, 32, "• " + $objectives[$id.to_i][j].to_s)
        else
          self.contents.draw_text(0, j * 32 + 224, 240, 32, "• " + $objectives[$id.to_i][j].to_s)
        end
      end
    end
    draw_quest_progress(96, 428, self.width - 128)
  end
 
  def update
    refresh
  end
 
end

class Window_Base < Window
 
  def draw_quest_progress(x, y, w = 200)
    current = $game_variables[$var_ID[$id.to_i]]
    ending = $end_val[$id.to_i]
    bordercolor = system_color
    outercolor  = Color.new(180, 210, 120, 255)
    midcolor    = Color.new(180, 210, 140, 255)
    innercolor  = Color.new(180, 210, 160, 255)
    emptycolor  = Color.new(0, 0, 0, 255)
    linewidth = (((current * 1.0) / ending) * (w - 2))
    emptywidth = ((w - 1) - linewidth)
    emptyx = ((x + 1) + linewidth)
    border = Rect.new(x, y, w, 8)
    emptyline = Rect.new(x + 1, y + 1, w - 2, 6)
    outerline = Rect.new(x + 1, y + 1, linewidth, 6)
    midline = Rect.new(x + 2, y + 2, linewidth - 2, 4)
    innerline = Rect.new(x + 3, y + 3, linewidth - 4, 2)
    self.contents.fill_rect(border, bordercolor)
    self.contents.fill_rect(emptyline, emptycolor)
    self.contents.fill_rect(outerline, outercolor)
    self.contents.fill_rect(midline, midcolor)
    self.contents.fill_rect(innerline, innercolor)
  end
 
end

class Scene_Save < Scene_File
 
  alias old_save_data write_save_data
  def write_save_data(file)
    old_save_data
    Marshal.dump($names, file)
    Marshal.dump($description, file)
    Marshal.dump($objectives, file)
    Marshal.dump($var_ID, file)
    Marshal.dump($end_val, file)
  end
 
end

class Scene_Load < Scene_File
 
  alias old_load_data read_save_data
  def read_save_data(file)
    old_load_data
    $names = Marshal.load(file)
    $description = Marshal.load(file)
    $objectives = Marshal.load(file)
    $var_ID = Marshal.load(file)
    $end_val = Marshal.load(file)
  end
 
end

class Scene_Title
 
  alias old_new_game command_new_game
  def command_new_game
    old_new_game
    $names.clear
    $description.clear
    $objectives.clear
    $var_ID.clear
    $end_val.clear
  end
 
end

class Scene_Menu
 
  def initialize(menu_index = 0)
    @menu_index = menu_index
    size = $names.size
    for i in 0..size
      var = $var_ID[i]
      ending = $end_val[i]
      if $game_variables[var.to_i] >= ending.to_i
        $names.delete_at i
        $description.delete_at i
        $objectives.delete_at i
        $var_ID.delete_at i
        $end_val.delete_at i
      end
    end
  end
 
end