“Does the unit need a sleeve and does a sleeve come with it? For the Frigidaire - Home Comfort 12,000 BTU Through-the-Wall Air Conditioner and 10,600 BTU Heater - White, Model: FFTH1222R2SKU: 9672155, does it require a sleeve? The picture implies the unit has a sleeve but the specs say "sleeve not included." So if I buy the unit, do I also need to buy the sleeve?”