[bug] native_write_to: no implicit conversion of nil into String

[larskanis]

Please describe the bug

XML::Node#write_to fails with no implicit conversion of nil into String

Happens on nokogiri-1.14.0-rc1 on Linux and Windows with binary gems, but not on nokogiri-1.13.10 or older versions.

Help us reproduce what you're seeing

doc=Nokogiri::XML("")
File.open("filename", "w") do |fd|
  doc.write_to(fd, :indent => 2)
end

With nokogiri-1.14.0-rc1:

/home/local/COMCARD-NT/kanis/.rvm/gems/ruby-3.1.3/gems/nokogiri-1.14.0.rc1-x86_64-linux/lib/nokogiri/xml/node.rb:1368:in `native_write_to': no implicit conversion of nil into String (TypeError)
	from /home/local/COMCARD-NT/kanis/.rvm/gems/ruby-3.1.3/gems/nokogiri-1.14.0.rc1-x86_64-linux/lib/nokogiri/xml/node.rb:1368:in `write_to'
        from /home/local/COMCARD-NT/kanis/.rvm/gems/ruby-3.1.3/gems/nokogiri-1.14.0.rc1-x86_64-linux/lib/nokogiri/html5/node.rb:37:in `write_to'
	from (irb):1:in `block in <top (required)>'
	from (irb):1:in `open'
	from (irb):1:in `<main>'
	from /home/local/COMCARD-NT/kanis/.rvm/rubies/ruby-3.1.3/lib/ruby/gems/3.1.0/gems/irb-1.4.1/exe/irb:11:in `<top (required)>'
	from /home/local/COMCARD-NT/kanis/.rvm/rubies/ruby-3.1.3/bin/irb:25:in `load'
	from /home/local/COMCARD-NT/kanis/.rvm/rubies/ruby-3.1.3/bin/irb:25:in `<main>'

Expected behavior

The script should write a file "filename" with content

<?xml version="1.0"?>

Environment

$ nokogiri -v
# Nokogiri (1.14.0.rc1)
    ---
    warnings: []
    nokogiri:
      version: 1.14.0.rc1
      cppflags:
      - "-I/home/local/COMCARD-NT/kanis/.rvm/gems/ruby-3.1.3/gems/nokogiri-1.14.0.rc1-x86_64-linux/ext/nokogiri"
      - "-I/home/local/COMCARD-NT/kanis/.rvm/gems/ruby-3.1.3/gems/nokogiri-1.14.0.rc1-x86_64-linux/ext/nokogiri/include"
      - "-I/home/local/COMCARD-NT/kanis/.rvm/gems/ruby-3.1.3/gems/nokogiri-1.14.0.rc1-x86_64-linux/ext/nokogiri/include/libxml2"
      ldflags: []
    ruby:
      version: 3.1.3
      platform: x86_64-linux
      gem_platform: x86_64-linux
      description: ruby 3.1.3p185 (2022-11-24 revision 1a6b16756e) [x86_64-linux]
      engine: ruby
    libxml:
      source: packaged
      precompiled: true
      patches:
      - 0001-Remove-script-macro-support.patch
      - 0002-Update-entities-to-remove-handling-of-ssi.patch
      - 0003-libxml2.la-is-in-top_builddir.patch
      - '0009-allow-wildcard-namespaces.patch'
      libxml2_path: "/home/local/COMCARD-NT/kanis/.rvm/gems/ruby-3.1.3/gems/nokogiri-1.14.0.rc1-x86_64-linux/ext/nokogiri"
      memory_management: ruby
      iconv_enabled: true
      compiled: 2.10.3
      loaded: 2.10.3
    libxslt:
      source: packaged
      precompiled: true
      patches:
      - 0001-update-automake-files-for-arm64.patch
      datetime_enabled: true
      compiled: 1.1.37
      loaded: 1.1.37
    other_libraries:
      zlib: 1.2.13
      libgumbo: 1.0.0-nokogiri

Additional context

[flavorjones]

Thanks for reporting! I'll take a look as soon as I can.