Show NULL values AS <NULL> not working

Hi Dave and team,

Another slight bug (I think):

I have a table which has a column called "first_invalid" which should be a
timestamp if the record is invalid, or NULL if it's valid.
In PgAdmin I have the "Show NULL values as <NULL>" option enabled, but it
still displays a blank cell for this column.

The reason why I think it may not be a bug, is I tried doing this:

"SELECT COALESCE(first_invalid, '<NULL>') AS first_invalid FROM table"

but PostgreSQL threw it out because "<NULL>" is not a valid timestamp -
instead I had to do:

"SELECT COALESCE(first_invalid, '1900-01-01') AS first_invalid FROM table"

to prove the column is in fact NULL, and I do get: "1900-01-01 00:00:00+00"
for this record, but in the data entry grid, PgAdmin still displays it
blank.

Question: is this a bug, or intended behaviour?

Thanks,

Andy