Mask value being setted as 0 if null

[Rui90]

I have this input using ui-mask

<input type="text" ui-mask-placeholder ui-mask="99999-999" ng-model="AddressPostalCode" name="AddressPostalCode">

But if I do not set a value, my scope will have the value 0, and this info will be sent. Why? Is there no simple way to if the mask is not correct or something, it just goes as null?