* lib/rexml/entity.rb (unnormalized): do not call
document.record_entity_expansion if document is nil.
see <http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=502535>.
Thanks, Naohisa Goto.
* test/rexml/test_document.rb: ditto.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_1@20182 b2dd03c8-39d4-4d8f-98ff-823fe69b080e