rexml 3.4.3 Document.new no longer accepts strings with no root element

[jrafanie]

Followup to ManageIQ/manageiq-gems-pending#614

We generally create the xml document and add the root element and others afterwards. This is ok, but we need to call REXML::Document.new(nil) instead. In 3.4.3 and future versions, it fails validation when the string provided to .new does not container a root element.

See the discussion in: https://www.github.com/ruby/rexml/pull/291

Note, this fixes the following errors with rexml 3.4.3:

  1) MiqAeClassController get selected Class/Instance/Method record back #get_class_node_info when the record exists returns class record and check count of override classes being returned
     Failure/Error: xml = REXML::Document.load("")

     REXML::ParseException:
       Malformed XML: No root element
       Line: 0
       Position: 0
       Last 80 unconsumed characters:
     # /Users/joerafaniello/.gem/ruby/3.3.9/gems/rexml-3.4.3/lib/rexml/parsers/baseparser.rb:271:in `pull_event'
     # /Users/joerafaniello/.gem/ruby/3.3.9/gems/rexml-3.4.3/lib/rexml/parsers/baseparser.rb:249:in `pull'
     # /Users/joerafaniello/.gem/ruby/3.3.9/gems/rexml-3.4.3/lib/rexml/parsers/treeparser.rb:21:in `parse'
     # /Users/joerafaniello/.gem/ruby/3.3.9/gems/rexml-3.4.3/lib/rexml/document.rb:466:in `build'
     # /Users/joerafaniello/.gem/ruby/3.3.9/gems/rexml-3.4.3/lib/rexml/document.rb:103:in `initialize'
     # /Users/joerafaniello/Code/manageiq-gems-pending/lib/gems/pending/util/xml/miq_rexml.rb:275:in `initialize'
     # /Users/joerafaniello/Code/manageiq-gems-pending/lib/gems/pending/util/xml/miq_rexml.rb:281:in `new'
     # /Users/joerafaniello/Code/manageiq-gems-pending/lib/gems/pending/util/xml/miq_rexml.rb:281:in `load'
     # ./app/controllers/miq_ae_class_controller.rb:404:in `build_details_grid'
     # ./app/controllers/miq_ae_class_controller.rb:2937:in `get_class_node_info'
     # ./spec/controllers/miq_ae_class_controller_spec.rb:355:in `block (5 levels) in <top (required)>'
     # /Users/joerafaniello/.gem/ruby/3.3.9/gems/webmock-3.25.1/lib/webmock/rspec.rb:39:in `block (2 levels) in <main>'

  2) MiqAeClassController#replace_right_cell Can build the AE tree
     Failure/Error: xml = REXML::Document.load("")

     REXML::ParseException:
       Malformed XML: No root element
       Line: 0
       Position: 0
       Last 80 unconsumed characters:
     # /Users/joerafaniello/.gem/ruby/3.3.9/gems/rexml-3.4.3/lib/rexml/parsers/baseparser.rb:271:in `pull_event'
     # /Users/joerafaniello/.gem/ruby/3.3.9/gems/rexml-3.4.3/lib/rexml/parsers/baseparser.rb:249:in `pull'
     # /Users/joerafaniello/.gem/ruby/3.3.9/gems/rexml-3.4.3/lib/rexml/parsers/treeparser.rb:21:in `parse'
     # /Users/joerafaniello/.gem/ruby/3.3.9/gems/rexml-3.4.3/lib/rexml/document.rb:466:in `build'
     # /Users/joerafaniello/.gem/ruby/3.3.9/gems/rexml-3.4.3/lib/rexml/document.rb:103:in `initialize'
     # /Users/joerafaniello/Code/manageiq-gems-pending/lib/gems/pending/util/xml/miq_rexml.rb:275:in `initialize'
     # /Users/joerafaniello/Code/manageiq-gems-pending/lib/gems/pending/util/xml/miq_rexml.rb:281:in `new'
     # /Users/joerafaniello/Code/manageiq-gems-pending/lib/gems/pending/util/xml/miq_rexml.rb:281:in `load'
     # ./app/controllers/miq_ae_class_controller.rb:404:in `build_details_grid'
     # ./app/controllers/miq_ae_class_controller.rb:2937:in `get_class_node_info'
     # ./app/controllers/miq_ae_class_controller.rb:195:in `get_node_info'
     # ./app/controllers/miq_ae_class_controller.rb:294:in `replace_right_cell'
     # ./spec/controllers/miq_ae_class_controller_spec.rb:872:in `block (3 levels) in <top (required)>'
     # /Users/joerafaniello/.gem/ruby/3.3.9/gems/webmock-3.25.1/lib/webmock/rspec.rb:39:in `block (2 levels) in <main>'

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48 examples, 2 failures

Failed examples:

rspec ./spec/controllers/miq_ae_class_controller_spec.rb:350 # MiqAeClassController get selected Class/Instance/Method record back #get_class_node_info when the record exists returns class record and check count of override classes being returned
rspec ./spec/controllers/miq_ae_class_controller_spec.rb:860 # MiqAeClassController#replace_right_cell Can build the AE tree