newPADOP()'s sv parameter is never NULL, so mark it as so.

newPADOP()'s sv parameter is never NULL, so mark it as so.
(Well, in theory it could be NULL if someone is creating ops during
symbol table destruction, but snowballs in hell, etc.
This is usually the point where Jarkko observes that the aliens are
looking for a free slot in their diaries...)

p4raw-id: //depot/perl@30034