pyqt - Include NoneType in Validator?

Question

I am adding a double validator for a qlineedit widget. But in reality the line might be empty, i.e. data is of NoneType. However in this case I don't want the validator to pop up a warning saying for example:

please type in values between 0.000 to 10000.000

Is there any way to add NoneType as an excluding instance when adding Validator?

Thanks very much!