Scheduler: Sessions disappear

[mariobehling]

Sessions disappear when the page is reopened or refreshed, e.g. all Blockchain sessions in the FOSSASIA Summit event are not showing up on the scheduler or on the left-side "to be scheduled" sidebar of the scheduler.

[iamareebjamal]

32 sessions got assigned a starts_at but no ends_at, hence they disappeared from both unscheduled and scheduled sessions. Reason X why allowing arbitrary PATCHes from client side is a bad idea. Anyway, unscheduled sessions should show sessions with either starts_at or ends_at null till it is known why they were assigned null ends at. This way at least they can be recheduled