(Bug 4719) Coerce all false values to the numerical 0

We can't rely on defined-ness. The cached value is stored as an empty string
when there are no points, so it fails the defined test and doesn't get set to
0. Then in the frontend it gets printed as an empty string...

This means that on production, or anywhere else with memcache on, first time
you load the page you'll get "you have 0 points". On subsequent loads it
becomes "you have points". Misleading! Annoying! Weird.