9.1rc1: TRAP: FailedAssertion("!(item_width > 0)", File: "costsize.c", Line: 3274)

I am developing against 9.1beta3 and encountered this problem. I repeated it against rc1 (or
actually, REL9_1_STABLE taken from git today).

The below SQL causes:

TRAP: FailedAssertion("!(item_width > 0)", File: "costsize.c", Line: 3274)

and the session crashes.

select *
from (
select
col1
, col2
, reviewed
from
(values
( 1111, 'aweyu', 3)
, ( 2222, 'bwetu', 2)
, ( 3333, 'vwxyz', 1)
)
as r(col1,col2,col3)
left join (
select 1 as reviewed, c2 from ( values ('abcde') ) as t1(c2)
union all select 0 as reviewed, c2 from ( values ('vwxyz') ) as t2(c2)
)
as up_all on up_all.c2 = r.col2
order by col3
)
as f
;

To simplify I used 'values' for the actual tables that I am using, but the above still causes the
FailedAssertion.

Removing the outer select avoids the error and
removing order by avoids the error

Erik Rijkers