code: protected void placeBecameEmpty ()
      {
          // let our delegates know what's up
          applyToDelegates(new DelegateOp(PlaceManagerDelegate.class) {
              @Override
              public void apply (PlaceManagerDelegate delegate) {
                  delegate.placeBecameEmpty();
              }
          });
  
  //         Log.info("Place became empty " + where() + ".");
  
          checkShutdownInterval();
      }
docs: Called when we transition from having bodies in the place to not having any bodies in the
  place. Some places may take this as a sign to pack it in, others may wish to stick
  around. In any case, they can override this method to do their thing.