re.c: check if onig_region_copy failed
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48669 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
re.c: check if onig_region_copy failed
memory exhausted but returns nothing, so check by if allocated.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48669 b2dd03c8-39d4-4d8f-98ff-823fe69b080e