merge revision(s) 53810: [Backport #12044]
* net/ftp.rb: add NullSocket#closed? to fix closing not opened connection. [Fix GH-1232]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@54330 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merge revision(s) 53810: [Backport #12044]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@54330 b2dd03c8-39d4-4d8f-98ff-823fe69b080e