fix scheduled reports not sending bug

it looks like c62a0a5020dc109124b497662c0be0c2e98d997f introduced
an issue where the default day for daily reports would sometimes get set
to `1` which would then not get returned by the couch view query which
was explicitly checking for `None`. this just ignores the day entirely.
Merge pull request #2513 from dimagi/scheduled-reports-fix

fix scheduled reports not sending bug