avoid rb_bug on BasicSocket.for_fd(-1)
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53231 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
avoid rb_bug on BasicSocket.for_fd(-1)
[ruby-core:72418] [Bug #11854]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53231 b2dd03c8-39d4-4d8f-98ff-823fe69b080e