Fix min/max integer param validation when either is 0.

Bug introduced in commit 5b4c4cf9bc9619d51d7f2471d64896dcdd93707c .
InRangeValidator would not be appended because self.min and self.max are no
more strings, but integers.

Reported by: Andrea Pinna <andrea.pinna@crs4.it>
Trackster: hide tool by default. Pack script.
Merge in stable to default