Inform that there are no rooms in the schedule

Inform that there are no rooms when creating the schedule with a message instead of creating a room with the title "No rooms". The message also include a link to the place where rooms are created.

app/controllers/admin/schedule_controller.rb

@@ -26,7 +26,7 @@ module Admin
       @unscheduled_events = @program.events - schedule.events
       @selected_schedule_id = @conference.program.selected_schedule.try(:id)
       @dates = @conference.start_date..@conference.end_date
-      @rooms = (@venue && @venue.rooms.any?) ? @venue.rooms : [Room.new(name: 'No Rooms!', size: 0)]
+      @rooms = @venue.rooms if @venue && @venue.rooms.any?
     end
 
     def update

app/views/admin/schedule/show.html.haml

@@ -5,7 +5,14 @@
       %p.text-muted
         Create the schedules for the conference
 
-.row
+- if @rooms.nil?
+  .h3
+    No Rooms!
+    %small
+      = link_to 'Create rooms', admin_conference_venue_rooms_path
+      before creating the schedule.
+- else
+  .row
     .col-md-2
       Selected schedule
       = check_box_tag @conference.short_title, @schedule_id, (@schedule_id == @selected_schedule_id),