How to check for / insert optional fields?

[eluser]wdm*[/eluser]
This doesn't seem to work for all data types.

Postgres doesn't let me save a '' (blank) value for a 'date' column type, for example.

Is this a Postgres bug?

[EDIT] On second thoughts, it seems more like a CI bug. Shouldn't $this->input->post return FALSE, or NULL, rather than an empty string?