fix self var
fix self var

FelikZ/node-steam-tradeoffer-manager,lpinca/node-steam-tradeoffers,nseckinoral/node-steam-tradeoffers,Alex7Kom/node-steam-tradeoffers,LorienMan/node-steam-tradeoffers,vejbuch/node-steam-tradeoffers,GoeGaming/node-steam-tradeoffers