Code review comment for lp:~widelands-dev/widelands/casern_workersqueue

This is WaresQueue does in the cleanup:

 if (filled_ && owner_.get_economy())
  owner_.get_economy()->remove_wares(index_, filled_);

 filled_ = 0;

etc...

I guess we should to the same for the workers queue now, since it's now more like the waresqueue and not like the soldercontrol?