hash.c, st.c: fix for ST_CHECK

* hash.c (foreach_safe_i, hash_foreach_iter): deal with error detected
  by ST_CHECK.
* st.c (st_foreach_check): call with non-error argument in normal case.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43674 b2dd03c8-39d4-4d8f-98ff-823fe69b080e