Update owner when assign children

lib/oga/xml/document.rb

@@ -46,6 +46,7 @@ module Oga
       # @param [Oga::XML::NodeSet|Array] nodes
       def children=(nodes)
         if nodes.is_a?(NodeSet)
+          nodes.owner = self
           @children = nodes
         else
           @children = NodeSet.new(nodes, self)

lib/oga/xml/node.rb

@@ -49,6 +49,7 @@ module Oga
       # @param [Oga::XML::NodeSet|Array] nodes
       def children=(nodes)
         if nodes.is_a?(NodeSet)
+          nodes.owner = self
           @children = nodes
         else
           @children = NodeSet.new(nodes, self)

spec/oga/xml/document_spec.rb

@@ -22,6 +22,7 @@ describe Oga::XML::Document do
       document.children = [child]
 
       expect(document.children[0]).to eq(child)
+      expect(document.children[0].parent).to eq(document)
     end
 
     it 'sets the child nodes using a NodeSet' do
@@ -31,6 +32,7 @@ describe Oga::XML::Document do
       document.children = Oga::XML::NodeSet.new([child])
 
       expect(document.children[0]).to eq(child)
+      expect(document.children[0].parent).to eq(document)
     end
   end