Tests fail with Nokogiri 1.13.7

[radar]

      TypeError:
        wrong argument type Nokogiri::XML::Element (expected Data)
      # ./lib/xmlsec.rb:7:in `sign!'
      # ./lib/xmlsec.rb:7:in `sign!'
      # ./spec/lib/nokogiri/xml/document/unsafe_xml_spec.rb:43:in `block (3 levels) in <top (required)>'

  58) unsafe xml guards: XML Signature URI does allow same document signing references
      Failure/Error: root.sign! opts

      TypeError:
        wrong argument type Nokogiri::XML::Element (expected Data)
      # ./lib/xmlsec.rb:7:in `sign!'
      # ./lib/xmlsec.rb:7:in `sign!'
      # ./spec/lib/nokogiri/xml/document/unsafe_xml_spec.rb:53:in `block (3 levels) in <top (required)>'

Just posting this here so you're aware.

I'll see if I can get a fix through.

Possibly related to #9?

[flavorjones]

👋 nokogiri maintainer here.

I wasn't aware of how much this gem (and potentially others) are relying on nokogiri internals. I've added this gem to our downstream test suite in sparklemotion/nokogiri#2595 so I'm aware of breakage that's being introduced.

I'd also like to offer up a PR to fix this ... give me a bit.