I haven't used qWidget yet but I know with qsVariable this was a gap in the input functionality that needed addressing.
Assuming that from the sound of it this hasn't been addressed yet then I would look to put some of my own logic into where im using my variables.
1. Set a default value for my variables in case a user doesn't input anything.
2. Do a validation check yourself on the content of the variable and if it fails replace with an appropriate value either the default or based on another variables logic that makes sense.