[gc_api] fix for retcontinuation pmc to avoid double-free
[gc_api] fix for retcontinuation pmc to avoid double-free

git-svn-id: 1eb33f31d1a165515dfa52993683d2778fcf3173@38650 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot