[sqlsmith] ERROR: partition missing from subplans

Hi,

running sqlsmith on REL_11_STABLE at 1b9d1b08fe for a couple hours
yielded the previously-unseen internal error "partition missing from
subplans".  It is readily reproducible on the regression database with
the following query:

select * from public.fk_partitioned_fk as sample_0 tablesample system (9.4)
   inner join public.money_data as sample_1
      on ((select pg_catalog.min(int_two) from public.test_type_diff2_c3) <> sample_0.a)
    where (sample_0.b is NULL);

                        QUERY PLAN
-----------------------------------------------------------
 Nested Loop
   InitPlan 1 (returns $0)
     ->  Aggregate
           ->  Seq Scan on test_type_diff2_c3
   ->  Seq Scan on money_data sample_1
   ->  Append
         ->  Sample Scan on fk_partitioned_fk_1 sample_0
               Sampling: system ('9.4'::real)
               Filter: ((b IS NULL) AND ($0 <> a))
         ->  Sample Scan on fk_partitioned_fk_3 sample_0_1
               Sampling: system ('9.4'::real)
               Filter: ((b IS NULL) AND ($0 <> a))

regards,
Andreas