fix for ISeq.of(method).
rb_method_iseq(method)
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66017 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
fix for ISeq.of(method).
rb_method_iseq(method)can return NULL.git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66017 b2dd03c8-39d4-4d8f-98ff-823fe69b080e