No it's a bug introduced in one of the PG 7.0 subversions, which
handles NULL wrong (NULLification should hold true for *all* types,
there should never be a "can't convert NULL" error).
This PG bug's fixed in PG 7.1 pre-beta, I tested it yesterday. By
coincidence I was working on this very same problem as someone else
e-mailed me a bug report about it a few days ago.
I'll be updating the CVS tree with about a 1/2 dozen or so bug fixes
for various things that you and others have posted about recently.
I'll not get everything fixed, but some things, at least...
I'll post an announcement and list of bug fixes when I get done.
