Remove needless nested parse exception information. [Bug #8844] [ruby-dev:47672] Reported by Ippei Obayashi. Thanks!!! * test/rexml/parser/test_tree.rb: Add a test for the above case. git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42813 b2dd03c8-39d4-4d8f-98ff-823fe69b080e