C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/novelconverter.rb:33:in `extensions_of_converted_files': undefined
method `ebook_file_ext' for nil:NilClass (NoMethodError)
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/command/convert.rb:198:in `block in convert_novels'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/command/convert.rb:181:in `each'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/command/convert.rb:181:in `with_index'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/command/convert.rb:181:in `convert_novels'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/command/convert.rb:162:in `block in execute'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/command/convert.rb:155:in `each'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/command/convert.rb:155:in `execute'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/commandbase.rb:107:in `execute!'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/commandbase.rb:115:in `execute!'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/command/update.rb:222:in `block (2 levels) in execute'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/command/update.rb:168:in `each'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/command/update.rb:168:in `each_with_index'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/command/update.rb:168:in `block in execute'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/narou_logger.rb:81:in `capture'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/command/update.rb:167:in `execute'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/commandline.rb:46:in `run'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/narou.rb:48:in `block in <top (required)>'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/lib/backtracer.rb:16:in `capture'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/narou.rb:47:in `<top (required)>'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/bin/narou:10:in `require_relative'
from C:/Ruby25/lib/ruby/gems/2.5.0/gems/narou-3.2.0.1/bin/narou:10:in `<top (required)>'
from C:/Ruby25/bin/narou:23:in `load'
from C:/Ruby25/bin/narou:23:in `<main>'