Add missing initializations of p_perminfo

In a61b1f7482, we failed to update transformFromClauseItem() and
buildNSItemFromLists() to set ParseNamespaceItem.p_perminfo causing
it to point to garbage.

Pointed out by Tom Lane.

Reported-by: Farias de Oliveira <matheusfarias519@gmail.com>
Discussion: https://postgr.es/m/3173476.1689286373%40sss.pgh.pa.us
Backpatch-through: 16

src/backend/parser/parse_clause.c

@@ -1573,6 +1573,7 @@ transformFromClauseItem(ParseState *pstate, Node *n,
 			jnsitem->p_names = j->join_using_alias;
 			jnsitem->p_rte = nsitem->p_rte;
 			jnsitem->p_rtindex = nsitem->p_rtindex;
+			jnsitem->p_perminfo = NULL;
 			/* no need to copy the first N columns, just use res_nscolumns */
 			jnsitem->p_nscolumns = res_nscolumns;
 			/* set default visibility flags; might get changed later */

src/backend/parser/parse_relation.c

@@ -1392,6 +1392,7 @@ buildNSItemFromLists(RangeTblEntry *rte, Index rtindex,
 	nsitem->p_names = rte->eref;
 	nsitem->p_rte = rte;
 	nsitem->p_rtindex = rtindex;
+	nsitem->p_perminfo = NULL;
 	nsitem->p_nscolumns = nscolumns;
 	/* set default visibility flags; might get changed later */
 	nsitem->p_rel_visible = true;