[sqlsmith] Failed assertion in postgres_fdw/deparse.c:1116

Creating some foreign tables via postgres_fdw in the regression db of
master as of de33af8, sqlsmith triggers the following assertion:
   TRAP: FailedAssertion("!(((((const Node*)(var))->type) == T_Var))", File: "deparse.c", Line: 1116)

gdb says var is holding a T_PlaceHolderVar instead.  In a build without
assertions, it leads to an error later:
   ERROR:  cache lookup failed for type 0

Recipe:

--8<---------------cut here---------------start------------->8---
create extension postgres_fdw;
create server myself foreign data wrapper postgres_fdw;
create schema fdw_postgres;
create user mapping for public server myself options (user :'USER');
import foreign schema public from server myself into fdw_postgres;
select subq_0.c0 as c0 from      (select 31 as c0 from fdw_postgres.a as ref_0      where 93 >= ref_0.aa) as subq_0
right join fdw_postgres.rtest_vview5 as ref_1      on (subq_0.c0 = ref_1.a )      where 92 = subq_0.c0;
 
--8<---------------cut here---------------end--------------->8---

regards,
Andreas