Fix compiler warning

Introduced by 41306a5, happens with gcc
4.7.2.

Author: petere

src/backend/catalog/objectaddress.c

@@ -1578,8 +1578,8 @@ get_object_address_opf_member(ObjectType objtype,
 	ObjectAddress address;
 	ListCell   *cell;
 	List	   *copy;
-	TypeName   *typenames[2];
-	Oid			typeoids[2];
+	TypeName   *typenames[2] = { NULL, NULL };
+	Oid			typeoids[2] = { InvalidOid, InvalidOid };
 	int			membernum;
 	int			i;