[BUG] Special characters (such as tab and space) do not correctly clean

[Glavin001]

See Glavin001/atom-beautify#16 (comment)

[Glavin001]

I have an object like the following:

{
  'indent_char': ' '
}

Where indent_char is a space character (' ').
After using nopt to clean, it is now an empty string, ''.
The same error occurs when using tab, '\t'.
Using underscore, '_', works as expected.