dir.c: fix FD leaks

* dir.c (do_opendir): close FD when fdopendir failed, e.g.,
  ENOTDIR.  [Feature#13056]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58912 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

dir.c

@@ -1372,11 +1372,11 @@ do_opendir(const int basefd, const char *path, int flags, rb_encoding *enc,
 #endif
 	    if (dirp) break;
 	    e = errno;
+	    /* fallback */
+	  case 0:
 #if USE_OPENDIR_AT
 	    if (fd >= 0) close(fd);
 #endif
-	    /* fallback */
-	  case 0:
 	    *status = 0;
 	    if (to_be_ignored(e)) break;
 	    if (errfunc) {