Sen

First thing is the scripts, but...
Does anyone know how to fix this error?

Script 'Window_SaveFile' line 74: NoMethodError occurred.

undefined method '[]' for nil:NilClass

It pops up at the save screen when I change the font for this game. I'm assuming this involves being unable to print Japanese text to the save-file screen. If I leave the font alone, it runs properly, but then the text is kind of ugly.

This is the default Main script:

unless Font.exist?("UmePlus Gothic")
print "UmePlus Gothic フォントが見つかりません。"
exit
end

begin
Graphics.freeze
PR.reading_system_data
Cache.pre_cache
$scene = Scene_Title.new
$scene.main while $scene != nil
Graphics.transition(30)
rescue Errno::ENOENT
filename = $!.message.sub("No such file or directory - ", "")
print("ファイル #{filename} が見つかりません。")
end

This is the Main script I used to success in Random Dungeon:

begin
Graphics.freeze
Font.default_name = ["UmePlus Gothic"]
Font.default_size = 20
$scene = Scene_Title.new
$scene.main while $scene != nil
Graphics.transition(30)
rescue Errno::ENOENT
filename = $!.message.sub("No such file or directory - ", "")
print("Unable to find file #{filename}.")
end

This is more or less just shouting into the void in frustration, but I'm hoping that someone might know what I should do.