[Appointments+] All new appointments have "Unknown" start time

The latest Appointments plugin update introduced the following item:
**Fixed a problem with appointments details, the start hour of appointment is now depended on settings.

Unfortunately, looks like it also broke something on the admin side, as click the details for any appointment shows the start time as "Unknown". This is the same for appointments created from the backend as well as those that we add manually using the appointments_insert_appointment function.