[Typo3-dev] NULL values in BE-Forms?

[Michael H.E. Roth]

Hi all,

I have an extension that needs NULL values in it's table. These are 
'tri-state' fields: yes, no, NULL.
How can I realize that?
I tried to define the field as int and in $TCA:
...
"tristatefield" => Array (
    "exclude" => 1,
    "label" => "LLL:EXT:...",
    "config" => Array (
        "type" => "radio",
        "items" => Array (
            Array("LLL:EXT:....0","NULL"),
            Array("LLL:EXT:....1","1"),
            Array("LLL:EXT:....2","0"),
        ),
        "default" => "NULL",
    )
),
...
Everything looks fine (data was and will be imported mainly by an external 
script) but when I try to edit the record for tri-state fields still being 
set to NULL are reported with an error that they cannot be written. :-(

Is this possible at all?

Thanks in advance for all tips and hints

Michael

--
Michael H.E. Roth