variable.c: check index overflow
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47512 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
variable.c: check index overflow
instance variable index overflow.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47512 b2dd03c8-39d4-4d8f-98ff-823fe69b080e