Should NaN be evaulated as empty?

[delzac]

<input type="text" _="on load get 'test' as a Number if it is empty set my value to 'NaN is empty' else set my value to 'NaN is not empty' end">

In the above test code, i try to convert a string into a number. This returns a NaN, but it doesn't evaluate as empty. I'm wondering if this behaviour is bug?