A checkbox-group option (woodoo_available_days) that gets saved with
nothing checked stores as '' rather than being absent, so get_option()'s
own default array never applies. (array) '' then casts to [''], intval
of '' is 0, and no weekday (1-7) ever equals 0 -- silently zeroing out
every single day, forever, with no visible error. Real incident on
cloudhost.es: the public booking CTA on informatiq.es always reported
'no available slots' for every date. Now explicitly falls back to the
Mon-Fri default whenever the stored value isn't a non-empty array.
Malin
eb173ca555