compile.c: check mid
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62041 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
compile.c: check mid
fix up r62039.
http://d.hatena.ne.jp/nagachika/20180125/ruby_trunk_changes_62025_62039#r62039
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62041 b2dd03c8-39d4-4d8f-98ff-823fe69b080e