Allow empty the field

[Daniel Tartarotti Sobrosa]

I have a situation that I need to apply a mask to the input, but it is important to allow the user to clear the field, putting the field on an "unset state".

[thenatsky]

This is a great little plugin. I'd like to be able to clear the field too, ie difference between 0 (an actual valid value in my use case) and null or ''