Invalid float

[Edwin]

Hello,

How is it possible to leave a FloatField empty?
Example:
When I edit a FloatField, delete its value (leaving its value empty) and post I get this message:

Project raised exception 'EConvertError' with message:
"" is an invalid float

I don't want to fill in 0 as a value. The FloatField has no DisplayFormat, is not required and is not a 'not null' field.
I am using ZeosDBO with Firebird 1.5.2.

Thanks,

Edwin