[perl #119351] fix B::CV::GV to return a B::SPECIAL on NULL

Cherry pick of

31d073689e2b5fa63aa7d4f8aaf529f75eeb5d0e
5f7c1602dfa694a4a6761e9e4fc077ce794f7ff0
f244b085582eaec9f2cf7bfabeb686bf74167bf6

combined with a version bump.