* lib/open-uri.rb (OpenURI.open_uri): Call StringIO#close only if
  the StringIO object is not closed yet.
  Reported by Jordi Massaguer Pla.  [ruby-core:42538] [Bug #6010]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45835 b2dd03c8-39d4-4d8f-98ff-823fe69b080e