psql --single-step mode doesn't like empty sets

As part of a 7.1.2->7.2 data migration process, I resorted to single stop
mode to see if I could determine the cause of an error (please see my
following post to this list).

$ less users.txt

COPY "users" FROM stdin;
\.
--
-- TOC Entry ID 71 (OID 604886)
--
-- Name: "element_name" Type: INDEX Owner: dan
--

$ psql --single-step fp2migration < users.txt
***(Single step mode: Verify
query)*********************************************
COPY "users" FROM stdin;
***(press return to proceed or enter x and return to
cancel)********************
ERROR: copy: line 1, CopyFrom: Fail to add null value in not null
attribute name
lost synchronization with server, resetting connection

Without single-stop, it works fine:
$ psql fp2migration < users.txt
$
--
Dan Langille
The FreeBSD Diary - http://freebsddiary.org/ - practical examples