[BUG] (firsttupleslot)==NULL is redundant or is possible null dereference?

[Ranier Vilela]

Hi,
This is real bug? firsttupleslot == NULL.

\backend\executor\nodeGroup.c
        if (TupIsNull(firsttupleslot))
        {
                outerslot = ExecProcNode(outerPlanState(node));
                if (TupIsNull(outerslot))
                {
                        /* empty input, so return nothing */
                        node->grp_done = true;
                        return NULL;
                }
                /* Copy tuple into firsttupleslot */
                ExecCopySlot(firsttupleslot, outerslot);

include\executor\tuptable.h:
#define TupIsNull(slot) \
        ((slot) == NULL || TTS_EMPTY(slot))

static inline TupleTableSlot *
ExecCopySlot(TupleTableSlot *dstslot, TupleTableSlot *srcslot)
{
        Assert(!TTS_EMPTY(srcslot));

        dstslot->tts_ops->copyslot(dstslot, srcslot);

        return dstslot;
}