Weapon Leveling Script Help

[Sinmora]

Ok, Ima newbie scripter and I've been playing around trying to get this script to work, anyway heres the code since Im kinda lazy. :O

Add this as a new script.

class Ultimate_Weapons
  
  attr_accessor :weapon_level
  attr_accessor :current_exp
  attr_accessor :max_exp
  attr_accessor :max_level
  attr_accessor :enemy_id
  
  def initialize
    @current_exp = 0  
    @weapon_level = 1
    troop = $data_troops[@troop_id]
    @enemy_id = troop.members[@member_index].enemy_id
    $ultimate_weps = Ultimate_Weapons.new
  end
 
#===================================================================
#-Weapon Leveling
#===================================================================
  

  def get_weapon
    return $game_actors[1].weapon_id
  end
  
  def monster_exp(enemy_id)
    case @enemy_id
    when 1
      return 25
    end
  end    
  
  def weapon_level_stats
    case @weapon_level
    when 1
      @max_exp = 100
    when 2
      @max_exp = 200
    when 3
      @max_exp = 300
    when 4
      @max_exp = 400
    end
  end
  
  def next_level?
    p "Current Exp: " + @current_exp.to_s + "Max Exp: " + @max_exp.to_s
    if $weapon_exp >= @max_exp
     @weapon_level += 1
   end
   if @weapon_level == 5
     @max_level = true
   else
     @max_level = true
   end
 end
end

Add this to Game_Enemy

  #--------------------------------------------------------------------------
  # - Acquisition of weapon experience
  #--------------------------------------------------------------------------
  def weapon_exp
    return 25 #25 is for test purposes
  end

Add this to Scene_Battle where it does things at the end of the battle.

bonus_weapon_exp = 0
bonus_weapon_exp += enemy.weapon_exp
actor2 = $game_enemy.weapon_exp
#-------------------------------------------------------------------------
#- Adds the weapon experience
#-------------------------------------------------------------------------
        actor2 += bonus_weapon_exp
#-------------------------------------------------------------------------
#- End adding the weapon experience
#-------------------------------------------------------------------------

Anyway, when you do a battle it all goes good until you end the battle.

Scene_Battle 2 - Line 73 - No Method Error
Undefined method 'weapon_exp' for nil:NilClass