[UI] Issue #102 - Clearing playlist details after deletion of last playlist.

We didn't properly handle a null case when there's no playlist left.  We
simply try to load the first playlist, but when no playlist is found,
there's a JavaScript error that simply causes the update to stop,
leaving the old data (last remaining playlist) populated.
[UI] Issue #103 - Off-by-one updating session entries, and a needed check upon re-load.

When we delete the last schedule, it doesn't properly remove.  We didn't
remove it from the user's PHP session because of an off-by-one, and when
we re-load the entries we didn't update properly either even though the
schedules file was properly updated to remove the entry.