Validation on empty field condition not working in fragment validator

Hi,

Please can someone advise why the validation on the || ! area_value condition does not work in the code below ?

if (area_value <= 0 || !area_value) {

return {
valid: false,
error: ‘Area value must not be empty or 0’
}
}
return true;

If I enter 0 or less than, I get the error. If I save the field without any value in it, I get no error! I’ve also tried:
area_value === ‘’
area_value === null

Neither work.

Version of Create is 2023.1

Thanks,

Mark