Ensure there's a corresponding time being dragged to
Ensure there's a corresponding time being dragged to

We were trying to calculate position of elements that didn't exist.
E.g. dragging an event to before 8.30am or after 7pm.

Also adjusts the 'boot' order to ensure `this.$el` is defined
before we add the row highlighter.

guidance-guarantee-programme/telephone_appointment_planner,guidance-guarantee-programme/telephone_appointment_planner,guidance-guarantee-programme/telephone_appointment_planner